The propulsion of mucus by cilia

Regulation of human airway surface liquid

Human airways are lined with a film of liquid from 5-100 microns in depth, consisting of a periciliary sol around and a mucous gel above the cilia. Microscopical studies have shown the sol to be invariably the same depth as the length of the cilia, and we discuss possible reasons for this. The composition and sources of the airway surface liquid are also described. In addition the forces regulating its volume are analyzed. Several airway diseases are characterised by dramatic changes in the volume and composition of airway liquid. We review recent research suggesting that the accumulation of airway mucous secretions in cystic fibrosis is caused by alterations in active transport of ions and water across both the surface and gland epithelia.

Primary ciliary dyskinesia (the immotile cilia syndrome)

OBJECTIVE

The purpose of this review is to familiarize the reader with the genetic aspects, clinical manifestations, diagnostic techniques and management of the primary ciliary dyskinesia syndrome. Further, this article illustrates some unusual features of this syndrome and discusses some speculative hypotheses concerning its pathogenesis and clinical presentation.

DATA SOURCES

The bibliography includes references in English as well as some references of historical interest in German. Both human and veterinary literature are quoted. Sources included computerized bibliographic searches of recent literature and reviews of literature.

STUDY SELECTION

Selection of papers was made based on their historic importance in the definition and characterization of the disease, and on reviews of large bodies of novel or interesting information. Some review papers were not included to avoid repetition.

RESULTS

Although the incidence of primary ciliary dyskinesia is low, the inclusion of this condition in the differential diagnosis of chronic and recurrent sinobronchial disease in children and older individuals is very common. Primary ciliary dyskinesia should be suspected in individuals who present chronic respiratory symptoms already in the neonatal period, develop profuse, chronic mucopurulent rhinorrhea, and chronic otitis media and sinusitis. Chronic cough, obstructive lung disease, and bronchorrhea associated with the aforementioned manifestations should also make clinicians suspect this syndrome. Male sterility is almost universally present and situs inversus is present in 50% of affected persons. The diagnosis of primary ciliary dyskinesia is clinical and is confirmed by studies of ciliary motility and ultrastructure of the respiratory mucosa. Management is directed to microbial suppression by frequent antibiotic administration, and to clearing of retained secretions.

CONCLUSIONS

The diagnosis of primary ciliary dyskinesia requires familiarity with the clinical picture and the specific techniques of identification. Although the basic mechanism of disease is known, the molecular genetics of primary ciliary dyskinesia and the causes for the phenotypic variability remain to be explained. Future research should be directed to the identification of the gene(s) responsible for the manifestations of the disease and to effective methods of activation, in vivo, of dysfunctional cilia.

The role of rheological properties in mucociliary transport by frog palate ciliated model

The effect of viscoelastic properties on mucociliary transport rate was investigated using the frog palate ciliated model. Mucociliary transportability of several hydrophilic polymeric gels with widely different viscoelastic characteristics were tested on the frog palate mucociliary model. An apparent negative relationship is observed between the relative transport rate (TR) and storage (G1) or loss (G2) modulus. However, a minimum in relative transport rate is observed at an apparent loss tangent (tan delta) value of between 0.7 and 0.9. A theoretical model for mucociliary transport is presented. The model predicted a minimum in transport rate at tan delta equal to 1.74 after adjustment for primary variation due to storage modulus (G1), which is in agreement with the observed frog palate transport rate. The model isolates the loss tangent (tan delta) and the magnitude of the complex modulus (magnitude of G*) as the important viscoelastic parameters for mucociliary transport. Optimum rheological characteristics with respect to slow transport rate can be achieved by using hydrophilic polymer gels with a large complex modulus and simultaneously with a loss tangent equal to 1.74.

Ex vivo technique for evaluating the effect of chemical vapours on mucociliary activity

An experimental protocol has been developed for the use of rat tracheal explant to evaluate the effects of inhaled chemicals on the mucociliary function. Rats were exposed for 4 h or 7 days (24 h per day) to different concentrations of toluene diisocyanate (TDI). Each rat trachea was subsequently removed rapidly and placed in a humid chamber maintained at 37 degrees C. Mucociliary function was evaluated by video measurements of the two following parameters: mucociliary beating frequency (MCBF) and number of active (A+), partially active (A +/-) and inactive areas (A-). In control tracheas; all areas were active and the MCBF showed hardly any variation around 15.3 Hz. In rats exposed to ca. 0.27 or 0.54 ppm of TDI for 4 h, tracheas showed a significant decrease in the number of active areas and a significant decrease in the MCBF. The same changes were observed in tracheas from rats exposed to approximately 0.05 and 0.10 ppm of TDI for 7 days. After a 7 days recovery period the number of active areas and the MCBF were similar in exposed and control rats except in the group exposed for 7 days to the highest concentrations; these showed only partial recovery. The results of this study showed that this ex vivo method is useful for detecting mucociliary dysfunction.

Host defence capacities of pulmonary surfactant: evidence for 'non-surfactant' functions of the surfactant system

The most well characterized function of pulmonary surfactant is its ability to reduce surface tension at the alveolar air-liquid interface, thereby preventing lung collapse. However, several lines of evidence suggest that surfactant may also have 'non-surfactant' functions: specific components of surfactant (proteins and phospholipids) may interact with different alveolar cells, inhaled particles and micro-organisms modulating pulmonary host defence systems. SP-A, the most abundant surfactant protein, binds to alveolar macrophages via a specific surface receptor with high affinity [128]. Such binding effects the release of reactive oxygen species from resident alveolar macrophages if SP-A is properly presented to the target cell. SP-A also stimulates chemotaxis of alveolar macrophages [142], and serves as an opsonin in the phagocytosis of herpes simplex virus [161] Candida tropicalis [138] and various bacteria [137]. In addition, SP-A enhances the uptake of particles by monocytes and culture-derived macrophages [140] and improves bacterial killing. SP-D, another hydrophobic surfactant-associated protein, might interact with alveolar macrophages as well, stimulating the release of oxygen radicals [148], while for the hydrophilic surfactant proteins SP-B and SP-C no macrophage interactions have been described so far. SP-A and SP-D are members of the so-called 'collectins', pattern recognition molecules involved in first line defence. While some surfactant proteins appear to stimulate certain macrophage defence functions, surfactant phospholipids seem to inhibit those of lymphocytes. Suppressed lymphocyte functions include lymphoproliferation in response to mitogens and alloantigens, B cell immunoglobulin production and natural killer cell cytotoxicity. Concerning surfactant's phospholipid composition phosphatidylglycerol is more suppressive than phosphatidylcholine on a molar basis [38]. Bovine surfactant has an immunosuppressive effect on the development of hypersensitivity pneumonitis in a guinea pig model [150]. Despite these interesting observations, several important questions concerning the interactions of surfactant components with pulmonary host defence systems remain unanswered. Sufficient host defence in the lungs works through various humoral-cellular systems in conjunction with the specific anatomy of the airways and the gas exchange surface--how does the surfactant system fit into this network? Surfactant and alveolar cells are both altered during lung injury--is there a relationship between alveolar cells from RDS patients and the endogenous surfactant isolated from such patients? How does exogenous surfactant as used for substitution therapy modulate the defence system of the host? Some of those artificial surfactants have been shown to inhibit the endotoxin-alveolar macrophages, PMNs and monocytes including IL-1, IL-6 and TNF [139,152].(ABSTRACT TRUNCATED AT 400 WORDS)

Pathophysiology of middle ear epithelium: a new role for prostaglandin E2

INTRODUCTION

Otitis media with effusion is a disease of the middle ear epithelium resulting from a decreased sol layer as well as increased mucus secretion and plasma-derived protein transudation, which causes mucus plugging. Because the epithelium keeps the middle ear cavities fluid-free and air-filled, we investigated its fluid transport capacities, which may be involved in both efficacy of the mucociliary clearance and drying-out of the posterior ear cavities (Yen PT et al: Acta Otolaryngol (Stockh) 113, 1993). We have established the absorptive capacity of middle ear epithelial cells in primary culture (Herman P, et al: Am J Physiol 262, 1992). However, the paucity of cells obtained by enzymatic digestion led us to develop a new model for further investigation of middle ear epithelial cell.

METHODS

We established a middle ear cell line (MESV) using simian virus 40 (SV40) infection of middle ear epithelial cells from the Mongolian gerbil.

RESULTS

Investigation of the transport processes using the short-circuit current technique showed that MESV cells retain most characteristics of the original middle ear epithelial cells. Transepithelial sodium transport from the apical to the basal side was responsible for the transepithelial lumen-negative potential difference.

CONCLUSION

The presence of high concentrations of prostaglandin E2 in the middle ear effusions has been documented. This work investigates the effect of prostaglandin E2 on the rate of transepithelial ion transport of MESV cells. Prostaglandin E2 increased the rate of electrogenic sodium transport by means of increase in the intracellular cyclic adenosine monophosphate (cAMP) content. Such a modulation of sodium transport in the course of otitis media could be responsible for the reduced periciliary sol layer that impairs the mucociliary clearance.

Simultaneous measurement of ciliary beating and intracellular calcium

A novel system for measuring, simultaneously, ciliary beating and intracellular free calcium is presented. The advantages and dynamic nature of the system are demonstrated by measuring the effects of the calcium ionophore lonomycin and of extracellular ATP on ciliated rabbit trachea. The results are discussed with regard to the ciliary and calcium stimulation.

Oxidant-mediated ciliary dysfunction in human respiratory epithelium

Exposure of human nasal ciliated epithelium to reactive oxidants generated by the enzymatic xanthine-xanthine oxidase superoxide/hydrogen peroxide (H2O2) and glucose-glucose oxidase H2O2-generating systems, or to reagent H2O2 or hypochlorous acid (HOCl) resulted in significant alterations in ciliary beating. The earliest change noted was the presence of ciliary slowing, progressing eventually to complete ciliary stasis in some areas. Ciliary dyskinesia was seen within the first hour, often from as early as 15 min after exposure of the cells to reactive oxidants. Using peroxidases, various antioxidant enzymes, and oxidant scavengers, we confirmed that these detrimental effects on ciliary function were mediated primarily by H2O2 and HOCl. Moreover, 3-aminobenzamide (3-ABA), an inhibitor of the DNA repair enzyme poly ADP ribose polymerase, prevented H2O2-mediated inhibition of ciliary function, indicating that oxidant-mediated damage to DNA may well be the basis of the effects of H2O2 on ciliated epithelium. Acute and chronic inflammatory responses may therefore present the possible threat of H2O2- or HOCl-inflicted injury on bystander respiratory epithelium, leading to ciliary dyskinesia and slowing.

Polymorphonuclear leukocyte-generated oxygen metabolites decrease beat frequency of human respiratory cilia

We investigated the effect of polymorphonuclear leukocyte (PMN)-generated oxygen metabolites on the ciliary beat frequency. PMNs were incubated with human respiratory cilia obtained by nasal brushing. The oxidative metabolism was stimulated by opsonized zymosan, and ciliary beat frequency was evaluated before and after activation of PMNs. Ciliary beat frequency was studied using video microscopy. Our results demonstrate a significant decrease in ciliary beat frequency after activation of PMNs. This effect was reduced by catalase. These data suggest that the PMN-generated oxygen metabolites, particularly H2O2, decrease beat frequency of human respiratory cilia.

The role of airway mucus in pulmonary toxicology

Airway mucus is a complex airway secretion whose primary function as part of the mucociliary transport mechanism is to to serve as renewable and transportable barrier against inhaled particulates and toxic agents. The rheologic properties necessary for this function are imparted by glycoproteins, or mucins. Some respiratory disease states, e.g., asthma, cystic fibrosis, and bronchitis, are characterized by quantitative and qualitative changes in mucus biosynthesis that contribute to pulmonary pathology. Similar alterations in various aspects of mucin biochemistry and biophysics, leading to mucus hypersecretion and altered mucus rheology, result from inhalation of certain air pollutants, such as ozone, sulfur dioxide, nitrogen dioxide, and cigarette smoke. The consequences of these pollutant-induced alterations in mucus biology are discussed in the context of pulmonary pathophysiology and toxicology.

In vitro transport of carbon in the trachea of veal calves

Carbon transport was studied in vitro in preparations of trachea and bronchus from veal calves. The mean velocity varied from 4.2 mm/min in the main bronchi to 6.3 mm/min in the ventral trachea. In some locations no transport was observed. Stereomicroscopic evaluation of Alcian blue-phloxine stained mucosal surfaces revealed differences in the appearance of the mucus layer between locations with and without mucus transport. It is concluded that quality and integrity of the mucus layer play an important role in mucus transport.

Metachronal activity of cultured mucociliary epithelium under normal and stimulated conditions

In the present work we measured in real time the metachronism and degree of correlation between beating cilia from cultured mucociliary epithelium. The method is based on simultaneous measurement of ciliary beat frequency, phase shifts, and correlation factors in two directions: parallel and perpendicular to the effective stroke direction (ESD). From the phase shifts the lengths of wave components, and consequently the metachronal wavelength and direction, were evaluated. On active ciliary areas of cultured frog esophagus under normal conditions, a relatively high degree of correlation is observed, but cilia are more correlated in direction parallel to ESD which is also the direction of the mucus propulsion. The length of the wave component parallel to ESD is more than twice as large as that of the perpendicular component. The metachronal wavelength was found to be in the range of 5-9 microns, and the direction of the wave propagation was in the range of 90 degrees-125 degrees clockwise to the ESD. When ciliary beat frequency was rapidly increased by extracellular ATP or acetylcholine, only minor effects were observed on the degree of correlation between beating cilia. The length of the wave component parallel to ESD showed the most dramatic effect increasing up to tenfold. The perpendicular to ESD component was not affected by the stimulation. Consequently, the metachronism became more laeoplectic with the angle between the ESD and the wave directions decreasing by 10 degrees-30 degrees, and the metachronal wavelength remained unaltered.

Variability in ciliary beat frequency in normal subjects and in patients with bronchiectasis

BACKGROUND

There is a wide variation in tracheobronchial clearance of inhaled aerosol in normal subjects and in patients with bronchiectasis, but little information is available on the variability in ciliary beat frequency (CBF).

METHODS

The variability in CBF was measured in 10 nasal mucosal samples from each of 19 normal controls and 23 stable bronchiectatic subjects.

RESULTS

The CBF varied at different mucosal sites in both normal subjects and bronchiectatic patients. Although the CBF of the fastest beating cilia was similar in both groups, the CBF of the slowest beating cilia was, on average, lower and showed greater within subject variation in bronchiectatic than in normal subjects.

CONCLUSIONS

There is a wide variation in CBF in nasal mucosal samples and this is significantly wider in bronchiectatic subjects with some cilia beating slowly. This may be a consequence of chronic inflammation or infection.

High-resolution CT in simple coal workers' pneumoconiosis. Lack of correlation with pulmonary function tests and arterial blood gas values

We examined 21 miners by means of standard chest radiography, high-resolution computerized tomography (HRCT), pulmonary function tests, and resting arterial blood gas levels. Using the ILO/UC classification of pneumoconiosis, 7 miners had category 1/0 or 2/1 simple coal workers' pneumoconiosis (CWP). By HRCT, nodules were identified in 12 miners; 4 of 9 were classified as category 0/0 CWP; 2 of 5, 0/1 CWP; 5 of 6, 1/0 CWP; and 1 of 1, 2/1 CWP by chest radiograph. Focal emphysema was identified by HRCT in 7 miners; 4 of 9 were classified as 0/0 CWP; 2 of 5, 0/1 CWP; and 1 of 6, 1/0 CWP by standard chest radiography. Four miners with definite nodules confirmed by HRCT had focal emphysema, while three without nodules had focal emphysema. Pulmonary function testing was not different between miners with or without CWP by standard chest radiography, nor was it different between miners with or without definite nodules evidenced by HRCT. No difference in resting oxygenation was found between any group of miners. The presence of focal emphysema confirmed by HRCT did not significantly affect pulmonary function tests on resting arterial blood gas values. There was, however, a significantly lower FEV1 and mean forced expiratory flow during the middle half of forced vital capacity with lifetime nonsmoking miners. The presence of CWP on chest radiography was significantly correlated with smoking cigarettes but not the years of mining. The presence of nodules on HRCT approached a significant correlation with cigarette smoking, but focal emphysema did not. For detecting evidence of coal dust accumulation in lung parenchyma and identifying focal emphysema, HRCT was more sensitive than standard chest radiography. However, despite earlier detection of parenchymal abnormalities, abnormal pulmonary function attributable to coal dust could not be identified.

Mucociliary function and endothelins 1, 2, and 3

Endothelins are recently discovered peptides that cause vasoconstriction and bronchoconstriction. The significance to the mucociliary system of endothelins (ET) 1, 2 and 3 in upper as well as lower airways has not yet been clarified. Effects of these active peptides were investigated, combining both in vitro and in vivo rabbit models of mucociliary activity from the maxillary sinus and the trachea. The studies were performed using computerized photometric microscopy. Immunohistologic staining procedures were used to determine the presence of endothelins in sinus and trachea epithelium. Significant effects on mucociliary activity were noted for ET-1, -2, and -3 in vitro as well as in vivo. All endothelins were noted to accelerate mucociliary activity of both sinus and tracheal mucosa. The effects of endothelins were greater in the sinus than in the trachea. In vitro studies using the calcium blocker nifedipine and the cyclooxygenase inhibitor diclofenac indicated that the mechanism of action involves an intermediary prostaglandin pathway but is independent of release of intracellular calcium. These results were confirmed using ET-1 in vivo. Immunohistochemical staining showed endothelin to be present in both maxillary and tracheal epithelium of the rabbit. We conclude that endothelins have significant mucociliary stimulatory effects and that the presence of endothelins in normal mucosa indicates a potentially important role in respiratory homeostasis as well as inflammatory conditions.

The role of hydrodynamic interaction in the locomotion of microorganisms

A general Boundary Element Method is presented and benchmarked with existing Slender Body Theory results and reflection solutions for the motion of spheres and slender bodies near plane boundaries. This method is used to model the swimming of a microorganism with a spherical cell body, propelled by a single rotating flagellum. The swimming of such an organism near a plane boundary, midway between two plane boundaries or in the vicinity of another similar organism, is investigated. It is found that only a small increase (less than 10%) results in the mean swimming speed of an organism swimming near and parallel to another identical organism. Similarly, only a minor propulsive advantage (again, less than 10% increase in mean swimming speed) is predicted when an organism swims very close and parallel to plane boundaries (such as a microscopic plate and (or) a coverslip, for example). This is explained in terms of the flagellar propulsive advantage derived from an increase in the ratio of the normal to tangential resistance coefficients of a slender body being offset by the apparently equally significant increase in the cell body drag. For an organism swimming normal to and toward a plane boundary, however, it is predicted that (assuming it is rotating its flagellum, relative to its cell body, with a constant angular frequency) the resulting swimming speed decreases asymptotically as the organism approaches the boundary.

Ciliary beat frequency in transplanted lungs

BACKGROUND

Patients with lung transplantation are prone to respiratory infections. Generally this is attributable to the effects of immunosuppressive drugs but mucociliary clearance has been found to be impaired in these subjects. A study was performed to determine whether this finding is accompanied by a reduction in ciliary beat frequency (CBF).

METHODS

Six patients who had undergone single lung transplantation for fibrosing lung disease were investigated. CBF was measured in mucosal samples from native and transplanted bronchi by a videophotometry method.

RESULTS

The CBF was reduced in the transplanted bronchi in all cases when both fastest and slowest beating cilia were examined. The fastest beating cilia on the native side had a mean (SD) CBF of 12.1 (1.3) Hz compared with 9.6 (2.0) Hz on the transplanted side. The slowest beating cilia also had reduced CBF on the transplanted side.

CONCLUSION

In patients with fibrotic lung disease, CBF is reduced in transplanted bronchi in comparison with native bronchi.

Epithelium-dependent responses of serotonin in a co-axial bioassay system

Serotonin (10(-6) - 10(-4) M) produced relaxations in a concentration-dependent (at 10(-6) and 10(-5) M concentrations) manner followed by a contraction (at 10(-4) M concentration) in a co-axial system, which consisted of guinea-pig trachea as a donor organ for epithelial derived-relaxing factor(s) and phenylephrine-precontracted rat anococcygeus muscle as assay tissue. Serotonin produced a concentration-dependent contraction only in precontracted rat anococcygeus muscle mounted alone or mounted co-axially within epithelium-denuded trachea. Indomethacin (10(-6) M) significantly inhibited the initial relaxations (from 25.1 +/- 7.8 to 7.8 +/- 5.0% and from 35.6 +/- 8.7 to 10.4 +/- 8.3% at 10(-6) and 10(-5) M concentrations of serotonin), but did not affect the contraction. Imipramine (10(-8) M) and hydrocortisone (3 x 10(-5) M) reduced the initial relaxations (from 20.5 +/- 1.6 to 3.8 +/- 1.5% and from 32.1 +/- 6.4 to 18.9 +/- 3.9% at 10(-6) M and 10(-5) M concentrations of serotonin, respectively) and also converted the serotonin (10(-4) M)-induced contraction to a relaxation. In the co-axial system with trachea from guinea-pigs previously sensitized with i.p. injected egg-ovalbumin, the serotonin-induced biphasic response was converted to a contractile response only after ovalbumin challenge. Histopathologic changes were observed in the epithelium of challenged tracheas taken from sensitized guinea-pigs and alterations of serotonin-induced epithelium-dependent responses were attributed to the morphological and/or functional damage of tracheal epithelium caused by ovalbumin challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Ion transport processes and middle ear physiopathology. An experimental approach using cell culture

The role of the middle ear (ME) epithelium is primarily to keep the cavities air-filled and fluid-free. This condition requires elimination of mucus and cellular debris from the tympanic cavity by the ciliary activity. This clearance activity may be related to active ion transport processes in the epithelium. This paper presents a review of the experimental data suggesting the existence of ion transports in ME, and demonstrating the contribution of the culture of ME epithelial cells to the investigation of ion transport properties. Primary cultures of ME epithelial cells from Mongolian gerbils (Meriones unguiculatus) were undertaken. Polarized monolayers exhibited domes on non-porous supports. On porous supports, the absorptive function was shown to be related to a Na+ absorption from apical to basal sides of the epithelium, by means of apical amiloride-sensitive Na+ channels and basolateral Na+, K(+)-ATPase. In turn, this sodium absorption would generate an osmotic gradient and drive a water flow. An amiloride-induced chloride transport is also suggested. A hormonal modulation of these ion transport properties might play a role in the development of the mucociliary impairment that initiates chronic otitis media. The establishment of a middle ea cell line using wild-type SV 40 infection is in progress. This might provide further information on the physiology of the ME.

Fluid and electrolyte transport by cultured human airway epithelia

An understanding of the fluid and electrolyte transport properties of any epithelium requires knowledge of the direction, rate, and regulation of fluid transport and the composition of the fluid. Although human airway epithelial likely play a key role in controlling the quantity and composition of the respiratory tract fluid, evidence for such a role is not available. To obtain such knowledge, we measured fluid and electrolyte transport by cultured human nasal epithelia. Under basal conditions we found that epithelia absorbed Na+ and fluid; both processes were inhibited by addition of amiloride to the mucosal surface. These data suggest that active Na+ absorption is responsible for fluid absorption. Interestingly, Na+ absorption was not accompanied by the net absorption of Cl-; some other anion accompanied Na+. The combination of cAMP agonists and mucosal amiloride stimulated the secretion of NaCl-rich fluid. But surprisingly, the response to cAMP agonists in the absence of amiloride showed substantial intersubject variability: cAMP stimulated fluid secretion across some epithelia, for others, cAMP stimulated fluid absorption. The explanation for the differences in response is uncertain, but we speculate that the magnitude of apical membrane Na+ conductance may modulate the direction of fluid transport in response to cAMP. We also found that airway epithelial secrete H+ and absorb K+ under basal conditions; both processes were inhibited by cAMP agonists. Because the H+/K(+)-ATPase inhibitor, SCH 28080, inhibited K+ absorption, an apical membrane H+/K(+)-ATPase may be at least partly responsible for K+ and H+ transport. However, H+/K+ exchange could not entirely account for the luminal acidification. The finding that cAMP agonists inhibited luminal acidification may be explained by the recent finding that cAMP increases apical HCO3- conductance. These results provide new insights into how the intact airway epithelium may modify the composition of the respiratory tract fluid.

Acute effect of inhaled bradykinin on tracheobronchial clearance in normal humans

BACKGROUND

Bradykinin, a nonapeptide that contributes as a mediator to the pathogenesis of asthma, may affect lung mucociliary clearance, as it has been shown to be a potent secretagogue in canine airways and in human nasal mucosa in vivo. To evaluate this possibility the effect of inhaled bradykinin on mucociliary clearance has been studied in 10 healthy volunteers.

METHODS

Subjects attended the laboratory on two occasions to take part in tracheobronchial clearance studies using a non-invasive radioisotopic technique. Inhalation of radioaerosol was followed 30 minutes later by inhalation of either bradykinin (8 mg/ml) or vehicle placebo in a randomised, double blind fashion. After each inhalation the number of coughs was recorded. Whole lung radioactivity was measured every half hour for six hours with two collimated scintillation counters, and a tracheobronchial clearance curve was plotted for each subject on each occasion.

RESULTS

Mucociliary clearance, expressed as the area under the tracheobronchial radioaerosol retention curve calculated for the first six hours (AUC0-6h), was greater in nine out of 10 subjects after inhalation of bradykinin than after placebo. The median values (range) for AUC0-6h were significantly reduced from 126% (78-232%)/h with placebo to 87% (51-133%)/h with bradykinin.

CONCLUSION

It is concluded that acute exposure to inhaled bradykinin accelerates tracheobronchial clearance in normal human airways.

Histochemical study of glycoconjugates in the nasal mucosa of the rat and guinea pig

A histochemical study was carried out on the glycoconjugates of the nasal mucosa of rat and guinea pig using conventional techniques and peroxidase-labelled lectins. Both the respiratory mucosa and neuroepithelium were studied. Sulphate and sialic acid groups were found in the mucous layer of the neuroepithelia, Bowman's glands and goblet cells. In contrast, the nasal glands did not possess these groups, and only a few showed neutral mucins. Carbohydrate residues were more numerous in the acini of the Jacobson glands. Thus, the nasal glands in the rat and guinea pig are probably of a serous type because of the scarcity of carbohydrate residues.

A study of the photoelectrical signal from human nasal cilia under several conditions

The movement of normal human nasal cilia was analyzed. Ciliary beat was recorded by means of a phase-contrast microscope equipped with a photodetector. The electrical signal was analyzed as follows: i) a power spectrum was calculated in order to measure ciliary beat frequency (CBF), ii) the beat cycles were averaged and the standard deviation of the waveform was computed to determine signal consistency (SC), and iii) the ratio of the duration of the smooth to that of the steep part of the cycles was measured. This was done under three different conditions: 1) normal or "initial", 2) after induction of "function loss", and 3) after "salbutamol stimulation". At "function loss," the cilia beat slower and with less harmony. CBF decreased from an average of 9.0 Hz in the "initial" condition to 5.8 Hz. SC decreased from an average of 5.7 to 1.9. After "salbutamol stimulation", average CBF was partially restored to 7.7 Hz, while average SC increased to 4.4. These findings indicate that in ciliary function studies, SC, as a measure for ciliary beat harmony, may be introduced alongside CBF as a second valuable parameter. In this study we were not able to identify different phases in the signal that might be used as a third parameter to indicate the effective and the recovery stroke.

Pollution: the nose and sinuses

The nose and sinuses are constantly exposed to the huge quantities of gases needed to maintain life. Not only is the human nose well-equipped to warm and humidify this inhaled air, but it is also uniquely able to clean much of it. Any material other than physiologic amounts of oxygen, nitrogen, carbon dioxide, and water that accompanies the airstream can be considered a pollutant, and this pollutant could potentially injure the individual. The following discussion will review the defense mechanisms that allow the nose and sinuses to protect the lower airways. The effects of pollutants on the respiratory mucosa will then be described, including some recent trends in those effects. These trends include specific population consequences of indoor and outdoor air pollution, and changes in risk for individuals in several occupations. Throughout these discussions, specific areas that would benefit from further research will be mentioned.

Assessment of bronchodilatation after spontaneous recovery from a histamine challenge in asthmatic children

BACKGROUND

It would be convenient to be able to measure airway responsiveness to histamine and to bronchodilator drugs on the same day, but whether this can be done reliably is unknown.

METHODS

The effect of a prior histamine challenge on the bronchodilator response to salbutamol after spontaneous recovery of FEV1 to 95% of the prechallenge level was studied in two groups of asthmatic children. Fourteen children inhaled 400 micrograms salbutamol after spontaneous recovery from a histamine challenge, followed by a further 100 micrograms salbutamol 20 minutes later. In a second group of eight asthmatic children the study was repeated with 800 micrograms salbutamol, followed by a further 200 micrograms 20 minutes later.

RESULTS

After histamine challenge FEV1 returned to baseline in 70 minutes or less on all occasions. The FEV1 20 minutes after 400 micrograms salbutamol was significantly lower after the histamine challenge than on the control day. After the further 100 micrograms salbutamol FEV1 values were similar after the histamine challenge and on the control day. FEV1 values after 800 micrograms salbutamol and the further 200 micrograms dose were not influenced by a prior histamine challenge.

CONCLUSIONS

In children with stable asthma in whom FEV1 has returned to baseline after a histamine challenge the FEV1 achieved after 800 micrograms salbutamol is not affected by the histamine challenge. Histamine and bronchodilator responsiveness can thus be assessed reliably on the same day in patients with stable asthma. This has clear advantages for patient care.

cAMP stimulates bicarbonate secretion across normal, but not cystic fibrosis airway epithelia

Adenosine 3',5'-cyclic monophosphate stimulates chloride (Cl-) secretion across airway epithelia. To determine whether cAMP also stimulates HCO3- secretion, we studied cultured canine and human airway epithelial cells bathed in a HCO3-/CO2-buffered, Cl(-)-free solution. Addition of forskolin stimulated an increase in short-circuit current that was likely a result of bicarbonate secretion because it was inhibited by a HCO3(-)-free solution, by addition of the carbonic anhydrase inhibitor, acetazolamide, or by mucosal addition of the anion channel blocker, diphenylamine 2-carboxylate. The current was dependent on Na+ because it was inhibited by removal of Na+ from the submucosal bathing solution, by addition of the Na+ pump inhibitor, ouabain, or by addition of amiloride (1 mM) to the submucosal solution. An increase in cytosolic Ca2+ produced by addition of a Ca2+ ionophore also stimulated short-circuit current. These data suggest that cAMP and Ca2+ stimulate HCO3- secretion across airway epithelium, and suggest that HCO3- leaves the cell across the apical membrane via conductive pathways. These results may explain previous observations that the short-circuit current across airway epithelia was not entirely accounted for by the sum of Na+ absorption and Cl- secretion. The cAMP-induced secretory response was absent in cystic fibrosis (CF) airway epithelial cells, although Ca(2+)-stimulated secretion was intact. This result suggests that HCO3- exist at the apical membrane is through the Cl- channel that is defectively regulated in CF epithelia. These results suggest the possibility that a defect in HCO3- secretion may contribute to the pathophysiology of CF pulmonary disease.

Intraepithelial airway dendritic cells: a distinct subset of pulmonary dendritic cells obtained by microdissection

Dendritic cells (DC), in general, and pulmonary DC, in particular, are a heterogeneous population of cells, their phenotype and function being dependent on their anatomic location, their state of activation, and the regulatory effect of locally secreted cytokines. Using a novel microdissection technique, the epithelium from the trachea and entire airway system was harvested, and the contained DC isolated at greater than 90% purity. The phenotype and function of these airway DC (ADC) was compared to DC isolated, at greater than 90% purity, from the parenchyma of the same lung. In contrast to lung DC (LDC), ADC did not express intercellular adhesion molecule 1 (ICAM-1) in situ, the amount of immune associated antigen (Ia) expressed was less (as determined by immunoperoxidase staining and immunopanning), and greater than 50% of ADC displayed Fc receptors (FcR). The majority of LDC were ICAM-1+, less than 5% expressed FcR, and all were intensely Ia+. Airway DC were most numerous in tracheal epithelium, but they were also present in small numbers in the epithelium of the most distal airways. Their numbers increased in all segments of the tracheobronchial epithelium in response to the administration of IFN-gamma. ADC were consistently more effective than LDC in presenting soluble (hen egg lysozyme) and particulate (heat-killed Listeria monocytogenes) antigens to antigen-sensitized T cells. By contrast, LDC were significantly more efficient in stimulating the proliferation of nonsensitized T cells in an autologous mixed leukocyte reaction. These data suggest that in normal animals, intraepithelial DC of airways share many attributes with Langerhans cells of the skin. Interstitial LDC, by contrast, reside in an environment where they may be exposed to a different set of regulatory factors and where they have progressed to a more advanced stage of differentiation than ADC. Both groups of DC are, however, heterogeneous, reflecting the continuous turnover that these cells undergo in the lung.

Humidification as an adjunct to chest physiotherapy in aiding tracheo-bronchial clearance in patients with bronchiectasis

Humidification of inspired air or oxygen is frequently utilized by respiratory physiotherapists to relieve sputum retention. Cold water, jet nebulizing humidifiers are in widespread use but there has been no previous attempt to investigate the efficacy of this treatment. We have performed a single-blind, cross-over study to quantify the effect of humidification as an adjunct to chest physiotherapy. Seven patients with bronchiectasis completed the trial, with a mean (range) age of 51 years (41-64 years) and mean (range) percent of predicted FEV1 of 46% (29-76%). On 2 days, separated by 1 week, subjects were randomly allocated to humidification or no humidification as a precursor to an optimal chest physiotherapy regimen. A radio-aerosol of human serum albumin millimicrospheres labelled with 99mTechnetium was used to measure sputum clearance by serial gamma camera images. Serial measurements of sputum weight and FEV1 were also recorded. Humidification (30 min) was followed by postural drainage (20 min) with the subject using the forced expiration technique to assist clearance. When humidification was combined with physiotherapy there was a significant increase in total wet weight of sputum (P less than 0.05) with a median (range) increase of 6 g (-9-15.5 g); and a significant increase in total radiolabel clearance (P less than 0.05) with a median (range) increase of 8.7% (1-13%), compared to physiotherapy alone. This study demonstrates that the use of cold water, jet nebulizing humidifiers significantly increases tracheo-bronchial clearance above that of an optimal physiotherapy regimen alone in bronchiectasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway epithelial cell mucin release: immunologic quantitation and response to platelet-activating factor

Mucus production is an integral component of airway mucosal inflammation. Platelet-activating factor (PAF) is a phospholipid mediator implicated in the pathogenesis of many inflammatory processes, including airway inflammation. PAF functions as a mucus secretagogue when mucus is quantitated as radiolabeled glycoconjugates released from airway organ cultures. To more directly assess the interaction of PAF and airway epithelial mucous cell secretion, we used primary feline tracheal epithelial cell cultures and an immunoassay for a specific mucous cell secretory vesicle component. Cultured tracheal epithelial cells were shown to synthesize and secrete glycoconjugates with mucin characteristics. These mucin-type glycoconjugates were immunoreactive with a mucous cell-specific antibody. Localization of this antibody to components of the secretory vesicles of cultured epithelial cells was confirmed by electron microscopic immunogold labeling. Using this monoclonal antibody, an immunoassay was developed to quantitate release of immunoreactive material into cell culture media. Exposure of cultures to PAF produced a concentration-dependent, prompt release of immunoreactive material. Concentration-dependent inhibition of this effect was demonstrated by coincubation with the PAF receptor antagonists, WEB 2086 and Ro 19-3704. A component of the signal transduction pathway for PAF effects was studied in cultured tracheal epithelial cells by coincubation of PAF with nordihydroguaiaretic acid (NDGA), a combined lipoxygenase and cyclooxygenase inhibitor, or p-bromophenacyl bromide (BPB), an inhibitor of cellular arachidonic acid release. Both NDGA and BPB blocked PAF-stimulated mucin release in a concentration-dependent manner. These studies demonstrate a direct airway epithelial mucous cell secretagogue effect that appears to be dependent upon airway epithelial PAF receptors and altered cellular lipid metabolism. These findings suggest a direct and potent mechanism for goblet cell secretion during airway inflammation.

Calcium regulation of ciliary beat frequency in human respiratory epithelium in vitro

1. The changes in ciliary beat frequency (CBF) of human nasal respiratory epithelial cells were measured in vitro with a photometric technique following exposure to either 4-bromo-calcium ionophore A23187 (4-Br-A23187) or trifluoperazine (TFP), an inhibitor of calmodulin-sensitive calcium-dependent protein kinases. Changes in intracellular free calcium concentrations in response to 4-Br-A23187 were studied using a fluorescent dye (Fura-2). 2. Addition of 10(-5) M-4-Br-A23187 caused a time-dependent (P less than 0.01) rise in CBF. The increment in CBF was statistically significant 10 min after challenge (+10%; P less than 0.01) and was sustained for at least 1 h, with maximal stimulation after 40 min (+ 18%; P less than 0.01). 3. Exposure to 10(-5) M-4-Br-A23187 caused an immediate increase in intracellular free calcium concentration, which preceded the rise in CBF. 4. TFP (10(-4) M) caused a reduction of baseline CBF (-10%; P less than 0.01) and prevented the expected rise when the cells were subsequently exposed to 10(-5) M-4-Br-A23187. 5. We conclude that: (1) calcium ionophore stimulates the CBF of human respiratory cells; (2) this effect is mediated through a calmodulin-sensitive system, since it is abolished in the presence of TFP; (3) the same pathway appears to control the basal CBF of these cells, since TFP also decreases CBF.

Mucus glycoproteins from cystic fibrotic sputum. Macromolecular properties and structural 'architecture'

Mucus glycoproteins (mucins) were isolated from sputum of patients with cystic fibrosis (CF) after separation into sol and gel phases. The mucus gel was solubilized with gentle stirring in 6 M-guanidinium chloride supplemented with proteinase inhibitors, and purification of mucins was subsequently achieved by isopycnic density-gradient centrifugation in CsCl/guanidinium chloride. Density-gradient centrifugation also revealed a heterogeneity of the macromolecules, the pattern of which varied between individuals, and mucins from the gel phase was pooled as 'heavy' and 'light' fractions. Gel chromatography on Sepharose CL-2B showed that the heavy fraction contained a larger proportion of smaller species than the 'light' fraction and that the gel phase mucins were much larger than those from the sol. An apparently homogeneous high-Mr mucin population from one individual contained approx. 70% (w/w) carbohydrate, the major sugars being N-acetylglucosamine (17.8%), N-acetylgalactosamine (6.7%), galactose (20.7%), fucose (13.2%) and sialic acid (11.4%). These mucins had an S020.w of 47 S, and an Mr of 15 x 10(6) -20 x 10(6), and rate-zonal centrifugation revealed a polydisperse size distribution [range (5-30) x 10(6)] with a weight-average Mr of 17 x 10(6). The whole mucins were visualized with electron microscopy as linear and apparently flexible threads, disperse in size. Reduction produced subunits which were included on Sepharose CL-2B, and subsequent trypsin digestion yielded high-Mr glycopeptides which were further retarded. The size distributions and fragmentation patterns of mucin from two other CF patients were the same, as studied by gel chromatography, rate-zonal centrifugation and electron microscopy. We conclude that CF mucins are heterogeneous in both size and buoyant density and that the various populations, though differing in buoyant density, share the same architecture and macromolecular properties and are, in this respect, similar to mucins from normal respiratory secretions [Thornton, Davies, Kraayenbrink, Richardson, Sheehan & Carlstedt (1990) Biochem. J. 265, 179-186] and human cervical mucus [Carlstedt & Sheehan (1989) SEB Symp. XLIII 289-316].

The release of a non-prostanoid inhibitory factor from rabbit bronchus detected by co-axial bioassay

1. Methacholine relaxed phenylephrine-contracted aorta of the rat with the endothelium intact. This effect was inhibited by haemoglobin, methylene blue, gossypol, phenidone and L-NG-nitroarginine methyl ester (L-NAME). Rat aorta denuded of endothelium failed to relax in response to methacholine, histamine and the peptidoleukotrienes C4, D4 and E4. 2. Methacholine and histamine but not leukotrienes C4, D4 and E4 relaxed phenylephrine-contracted rat aorta without endothelium when surrounded by rabbit epithelium-intact bronchus. The muscarinic antagonist atropine antagonized the methacholine-induced relaxation. 3. Removal of the epithelium either mechanically or chemically, abolished methacholine-induced relaxation of rat aorta in the co-axial bioassay. These data indicate that the epithelium is responsible for the observed relaxant effect to methacholine and histamine. 4. The cyclo-oxygenase inhibitor, indomethacin, the phospholipase A2 inhibitor, mepacrine and the lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA), failed to inhibit methacholine-induced relaxation of rat aorta in the co-axial bioassay. This indicates that the epithelium-derived inhibitory factor (EpDIF) is not a product of the cyclo-oxygenase or lipoxygenase pathway or a product derived from activation of phospholipase A2. 5. Haemoglobin, methylene blue, phenidone, gossypol and L-NAME failed to inhibit the relaxation of rat aorta in the co-axial bioassay. These results demonstrate that EpDIF detected in the co-axial bioassay is not endothelium-derived relaxing factor (EDRF) or nitric oxide. Similarly, catalase was without effect. 6. EpDIF is unlikely to be a peptide since papain and alpha-chymotrypsin failed to alter the methacholine-induced relaxation of rat aorta in the co-axial bioassay. Furthermore, thiorphan, captopril and aprotinin were also without effect, suggesting that EpDIF is not a substrate for airway peptidases. 7. The results presented in this paper demonstrate the release of a vasoactive epithelium-derived inhibitory factor (EpDIF) from rabbit intrapulmonary bronchi by use of a co-axial bioassay preparation.

Ciliary activity and pollution

The mucociliary clearance is an important part of the nonspecific defense mechanism of the human airways. Coordinated beats of cilia in the nose, trachea, and bronchi propel the mucous layer toward the pharynx, and with it inhaled microorganisms and other particles captured in the mucus. Normal function of this system depends on the efficacy of the ciliary beating and the properties of mucus. Primary ciliary dyskinesia--a congenital respiratory disease characterized by ultrastructural defects and motility disturbances of cilia--has provided us with valuable information about the role the mucociliary function plays in the protection against harmful agents in the inhaled air. Secondary ciliary dyskinesia is described in inflammatory disorders of the respiratory tract, but also some components in air pollution results in malfunction of cilia, damage of ciliated epithelium, or alteration in the mucus. This review will focus on investigations found in the literature concerning the influence of pollutants on ciliary activity. The methods applied will be evaluated.

Long-term drug treatment of asthma in children

In this short review the pharmacologic and clinical effect of antiasthma drugs in children that is, beta 2-agonists, theophylline, anticholinergics, disodiumcromoglycate/nedocromil sodium, and inhaled corticosteroids are described. Furthermore, a medication plan for maintenance treatment is presented.

Expression of mucin synthesis and secretion in human tracheobronchial epithelial cells grown in culture

The effects of culture conditions on growth and differentiation of human tracheobronchial epithelial (HTBE) cells have been defined. Epithelial cells were dissociated from tissues by protease treatment and were plated on tissue culture dishes in F12 medium supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, cholera toxin, bovine hypothalamus extract, and retinol. HTBE cells did not express any mucociliary function (ciliogenesis or mucin secretion) on tissue culture plastic, but they could be passaged 3 to 5 times with a total of 10 to 25 population doublings. Cells from early passages re-express both these functions when transplanted to tracheal grafts. When tissue culture plates were coated with collagen film or collagen gel substrata, cell attachment and proliferation were stimulated. However, the expression of mucous cell function in culture occurred only when cells were plated on collagen gel substrata and vitamin A (retinol) was present in the medium. Mucous cell differentiation under optimal conditions was defined by ultrastructural studies, by immunologic studies with mucin-specific monoclonal antibodies, and by carbohydrate and amino acid compositional analyses of mucin-like glycoproteins purified from culture medium. These results demonstrate for the first time that HTBE cells can express mucin synthesis and secretion under appropriate culture conditions.

Mucociliary clearance from central airways in patients with excessive sputum production with and without primary ciliary dyskinesia

Studies of mucociliary clearance were made on 17 patients with bronchiectasis and excessive sputum production. Tracheal mucus velocity was measured. Five patients with primary ciliary dysfunction and 12 who had no clinical evidence of this defect were studied. The mean (+/- SD) tracheal mucus velocity of the five patients with proved or presumptive primary ciliary dysfunction was 2.9 +/- 0.2 mm per minute and for the 12 patients without ciliary dysfunction, 7.9 +/- 1.4 mm per minute. (The previously determined rate for normals was 4.7 +/- 1.3 mm per minute.) In four of five patients with ciliary dysfunction, CBF was below 7.5 Hz while in the one patient of the 12 without ciliary dysfunction CBF was at the lower limit of normal values. Thus, mucociliary clearance responds to load, depends partly on CBF, and has a built-in control system and the means for compensating for ciliary dysfunction.

The effect of some preservatives used in nasal preparations on the mucus and ciliary components of mucociliary clearance

Efficient mucociliary clearance is a function of the physical properties of the mucus coupled to appropriately functioning cilia and may be altered by substances affecting ciliary beat frequency (CBF). Therefore the effect of preservatives on CBF was investigated using a photoelectronic technique. Methyl-p-hydroxybenzoate, propyl-p-hydroxybenzoate, chlorbutol and chlorocresol inhibited beat frequency, an effect which was reversible upon rinsing out the first three compounds but not chlorocresol. The effect of chlorhexidine and phenylmercuric borate on CBF was complicated by an interaction with chloride ions in the media used. EDTA did not appear to be ciliotoxic, while the effect of benzalkonium chloride was variable. Thiomersal halted ciliary beating after 40-100 min. Mucociliary clearance may also be affected by an alteration of the physical properties of the mucus layer, therefore the effect of each compound on the rheological properties of purified pig gastric mucus glycoprotein was investigated. None of the preservatives significantly altered the viscoelastic properties of the gel, measured using dynamic techniques.

Airway epithelium-derived inhibitory factor

Various bronchoactive agents can induce the release from the airway epithelium of an inhibitory substance that is able to relax certain tissues including rat aorta and possibly also airway smooth muscle. This substance, whose existence has recently been confirmed using a new bioassay system, is distinct from nitric oxide (EDRF) and is also known to be non-prostanoid in nature. Roy Goldie and colleagues describe the properties of this factor, and its potential clinical significance.

Effects of chest physical therapy on lung function in children recovering from acute severe asthma

The effects of chest physical therapy in acute severe asthma in children have been studied in 38 children aged 6 to 13 years in a randomized placebo controlled trial. The study began between 6 and 24 hours after admission to hospital; 19 children received chest physical therapy (PT) and 19 children received placebo visits. Each child had 4 treatments over 2 days which were preceded by nebulized salbutamol. Lung volumes and flow rates were measured in a body plethysmograph before salbutamol and before and after either PT or placebo on the first and fourth treatments. Throughout the study standard asthma drug therapy was given. In both groups characteristics such as sex, race, age, height, weight, severity, and baseline lung function were similar. Taking into account the baseline, lung function at the end of the study was similar in both groups. Three 12 year old children in the PT group showed improvements in flows above those seen in any children in the placebo group. We conclude that chest PT, when combined with asthma drug therapy, does not improve lung function in most children in this age group with acute severe asthma.