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PubMed1986

Biosynthesis, processing and secretion of mucus glycoprotein in the rat stomach.

For the study of the biosynthesis, processing and secretion of mucus glycoproteins in rat gastric mucous cells, antibodies were raised against purified gastric mucus glycoproteins and against deglycosylated gastric mucus glycoproteins. Indirect immunofluorescence analysis of gastric mucosa sections revealed that both antibodies specifically labelled the mucus glycoprotein-synthesizing cells in the gastric mucosa. Stomach segments were pulse-labelled with [35S]cysteine and chased for various times. The radioactively labelled (glyco)proteins were quantitatively immunoprecipitated and analyzed by SDS-polyacrylamide gel electrophoresis. Less than 3% of the total radioactivity incorporated in protein was found to be present in mucus glycoproteins. Antibodies raised against native mucus glycoproteins recognized only high-molecular-weight mucus glycoproteins, while the antibodies against deglycosylated glycoproteins also bound to probable precursor forms. The synthesis of mature mucus glycoproteins (Mr greater than 300 000) required about 90 min. After 3 h of chase, only a small portion of the pulse-labelled mucus glycoproteins had been secreted; the majority of the radioactive glycoproteins at that time was still associated with the tissue. Immature (glyco)proteins were not secreted into the medium.

Animals↗
PubMed1986

Stimulatory effect of enprostil, an anti-ulcer prostaglandin, on gastric mucus secretion.

Enprostil, a synthetic analogue of prostaglandin E2, is known to be a potent inhibitor of gastric acid secretion, and has marked anti-ulcer activity in rodents. Enprostil was administered in doses ranging from 15 to 250 micrograms/kg to rats prepared using the Shay procedure. Three hours later, the rats' stomachs were removed and processed either for the chemical determination of mucus, or for scanning electron microscopy. For the chemical determination, the secreted gastric juice was removed and the adherent gastric mucus was eluted with 2 M sodium chloride. The anthrone method was used to determine the mucus present. Enprostil was found to significantly increase gastric mucus at a dose of 60 micrograms/kg when measured by the anthrone test. Enprostil administered by the oral route was most effective in stimulating mucus secretion, suggesting a local or topical action of enprostil on mucus-secreting cells. Scanning electron microscopy of rat fundic mucosa after enprostil administration (50 to 100 micrograms/kg) revealed the presence of thin veil-like layers covering the epithelial surface, which was interpreted as an increase in mucus secretion. Higher magnifications (X 2,000) clearly showed the layers of mucus covering the surface epithelial cells. Enprostil's apparent increase of gastric mucus secretion may contribute to its anti-ulcer activity and may promote gastric healing.

Administration, Oral↗
PubMed1983

Retardation of hydrogen ion diffusion by gastric mucus constituents: effect of proteolysis.

The role of mucus glycoprotein, lipid and protein in the retardation of hydrogen ion diffusion by dog gastric mucus was investigated. The uniform layer of mucus (1.0 +/- 0.2mm thick), formed on the sintered glass support placed between equimolar (0.155M) solutions of HCl and NaCl, caused a 73% reduction in hydrogen ion diffusion when compared with a layer of NaCl. The rate of hydrogen ion diffusion through purified mucus glycoprotein was similar to that of native mucus, whereas a 30% increase in permeability of glycoprotein to hydrogen ion was observed following its delipidation. Preincubation of the purified mucus glycoprotein with serum albumin or IgA led to an increase in the ability of glycoprotein to retard the diffusion of hydrogen ion. This effect of albumin and IgA occurred at a physiological dose. About 70% decrease in hydrogen ion retardation was obtained following digestion of purified mucus glycoprotein with pepsin, and 74% following its digestion with pronase. The results show that the ability of gastric mucus to retard the diffusion of hydrogen ion depends upon the polymeric structure of undegraded mucus glycoprotein and the extent of interaction of this glycoprotein with lipids, serum albumin, and secretory IgA.

Animals↗
PubMed1997

Quantification of immunoglobulin in the serum and mucus of channel catfish at different ages and following infection with Edwardsiella ictaluri.

An enzyme-linked immunosorbent assay was developed to quantify immunoglobulin (Ig) in the serum and mucus of channel catfish (Ictalurus punctatus). The capture antibody (Ab) was a monoclonal Ab to channel catfish Ig and the detector was a polyclonal goat serum against channel catfish Ig. Detectable levels of channel catfish Ig were 0.1 microgram ml-1 and coefficients of intra- and interassay variations were 20% and 15%, respectively. Serum Ig concentration was found to increase from 0.36 +/- 0.25 to 0.49 +/- 0.26 mg ml-1 between 3 and 15 months of age. In contrast, mucus Ig concentration slightly decreased from 0.55 +/- 0.52 to 0.45 +/- 0.82 ng cm-2 of skin between 3 and 15 months of age. Mucus Ig concentrations were highest immediately caudal to gill covers and between pectoral to anal fins, at concentrations of 0.45 +/- 0.82 and 0.34 +/- 0.67 ng cm-2, respectively. The concentration of mucus Ig between anal and caudal fins and on the ventral skin between gill covers and pectoral fin was 0.18 +/- 0.42 and 0.09 +/- 0.14 ng cm-2, respectively. The kinetics of Ig production following infection with Edwardsiella ictaluri showed that serum Ig concentrations markedly increased (20.92 +/- 32.75 mg ml-1) at 13 days post-infection. The increase in mucus Ig concentrations occurred 14 days later (0.80 +/- 1.91 ng cm-2). Individual variation in both serum and mucus Ig production increased considerably during the course of infection (+/-0.23 to +/-32.75 mg ml-1 for serum Ig and +/-0.1 to +3.41 ng cm-2 for mucus Ig). The results suggest that E. ictaluri infection causes higher Ig production than that found in non-infected fish of the same age. Ab response to E. ictaluri was detected in the serum but not in the mucus of infected fish. Our results show differences in serum and mucus Ig concentrations with age and after infection with E. ictaluri.

Aging↗
PubMed1993

A glycosulphatase that removes sulphate from mucus glycoprotein.

A novel glycosulphatase has been purified from a mucus glycopeptide-degrading Prevotella from the colon. The purified enzyme removed inorganic [35S]sulphate from 35S-labelled native rat gastric mucus glycoprotein. Desulphation of mucus glycoprotein was initially rapid (19% complete after 10 min) but then plateaued, reaching only 33% after 3 h. Crude periplasmic extracts could remove 79% of the radioactivity as inorganic sulphate. These results suggest that steric hindrance may limit the access of the purified glycosulphatase to the mucus glycoprotein oligosaccharide chains in the absence of glycosidases, and/or that the enzyme may have the wrong specificity for some of the remaining sulphated sugars in the chains. The apparent molecular mass of the enzyme was 111 kDa as judged from gel exclusion chromatography, and it appeared to be composed of two identical subunits. The enzyme was localized in the periplasm of the bacterium, and using pig gastric mucus glycopeptide as a growth substrate markedly increased enzyme levels. Enzymic activity increased at the end of the growth phase. The substrate specificity of the enzyme was tested against low-molecular-mass sulphated molecules. The monosaccharides glucose 6-sulphate and N-acetylglucosamine 6-sulphate were rapidly desulphated, the latter being the major sulphated sugar in some mucus glycoproteins. Lactose 6-sulphate, galactose 6-sulphate, sulphated steroids and unsaturated disaccharide sulphate breakdown products from chondroitin sulphate were not desulphated. Glycosulphatases which can remove sulphate from mucus glycoproteins may play an important role in the degradation of highly sulphated mucus glycoproteins in the digestive tract, and could modify the effectiveness of mucus glycoproteins in mucosal protection.

Animals↗
PubMed1996

Isolation and characterization of Pseudomonas aeruginosa genes inducible by respiratory mucus derived from cystic fibrosis patients.

Pseudomonas aeruginosa, an opportunistic human pathogen, is a major causative agent of mortality and morbidity in immunocompromised individuals and those with cystic fibrosis (CF). In CF patients, the secretion of abnormally high amounts of mucus into the airways contributes to their susceptibility to infection by P. aeruginosa. To identify virulence genes of P. aeruginosa that are important in infection of CF patients, an in vivo selection system (IVET) was used to identify promoters that are specifically inducible by respiratory mucus derived from CF patients. Three genetic loci that are highly inducible by the mucus were identified. One of them is a well-characterized virulence gene (fptA), encoding the receptor for pyochelin, which is a P. aeruginosa iron siderophore. Induction of the fptA gene by mucus is suppressed by the addition of exogenous iron, demonstrating that the mucus is an iron chelator and generates an iron-deficient environment in CF lungs. Therefore, as a part of the host-defence mechanism, the mucus could also be responsible for induction of iron-regulated virulence factors of bacterial pathogens. The second locus, np20, encodes a peptide that shares sequence homology to a number of transcriptional regulators. An identical locus was previously identified to be inducible in vivo during infection of mice and was shown to be important in bacterial virulence in a neutropenic-mouse infection model. The third locus, designated migA (mucus inducible gene), was sequenced and found to encode a 299-amino-acid peptide which is homologous to glycosyltransferases of other bacteria, and is involved in the biosynthesis of lipopolysaccharides or exopolysaccharides. Inducibilities of the np20 and migA genes are not affected by iron and the exact nature of the inducing signals in the mucus is not known. The possible implications of the migA inducibility by respiratory mucus is discussed in relation to the P. aeruginosa infection in CF.

Amino Acid Sequence↗
PubMed2003

Colonic mucus: secretion and turnover in relation to dietary fibre intake.

The colon is subjected to a myriad of potentially damaging agents that may reside within the lumen for 1-2 d. Its first line of defence against these agents is the protective mucus bilayer that lines the entire colonic mucosa. This bilayer acts as a physical barrier to mucosal aggressors and also reduces shear stress to the mucosa. These actions are dependent on the unstimulated ('resting') colonic mucus thickness, and also on the rate that this layer can be replenished. The colonic mucus layer is altered in a number of colonic diseases that have been linked to a deficiency of fibre in the diet. The action of fibre intake on colonic mucus thickness and secretion is unknown. Using an in vivo rat model it has been demonstrated that: (1). fibre deficiency leads to a decreased protective potential of the mucus layer (e.g. the mean resting mucus thickness of the fibre-deficient group (429 microm) was significantly lower than its respective control (579 microm; P< 0-001), as was its total mucus secretion over 6 h (270 microm v. 541 microm; P<0-01); (2). specific fibre types in the diet alter the secretion dynamics of colonic mucus (e.g. a cellulose-based diet reduces total mucus secretion over 6 h compared with its control (175 microm v. 463 microm). Analysis of the diets suggested a necessity for both soluble and insoluble fibre types in the diet to increase mucosal protection.

Animals↗
PubMed1999

Comparison of human cervical mucus and artificial sperm penetration media.

The cervical mucus penetration tests aid research and determine the clinical importance of positive sperm antibody tests. Limited availability and variability of human cervical mucus have instigated the search for mucus substitutes for these tests. This study compares sperm migration in cervical mucus with that in artificial media including hyaluronate solution, egg white and albumin Tyrode solution. Results were quantified by measuring the migration distance (the maximum distance of capillary migration from a semen reservoir by spermatozoa after 1 h) and the sperm concentration at half the migration distance. The mean of both measures for cervical mucus and hyaluronate solution were equivalent [4.4 +/- 1.1 (SD) versus 4.3 +/- 1.0 cm and 118 +/- 51 versus 111 +/- 44x10(3)/ml], and higher than in egg white and albumin Tyrode solution. Antisperm antibodies impaired sperm penetration in cervical mucus and hyaluronate solution in a similar manner (r = 0.92). These results suggest that hyaluronate solution sufficiently resembles human cervical mucus in terms of penetrability that it may be used as a substitute for mucus in capillary tube tests of sperm function. The higher penetrability of cervical mucus and hyaluronate solution is probably related to a channelling effect due to their polymeric structure.

Albumins↗
PubMed2003

How Helicobacter pylori urease may affect external pH and influence growth and motility in the mucus environment: evidence from in-vitro studies.

BACKGROUND: Survival of Helicobacter pylori is dependent upon urease in the cytoplasm and at the bacterial surface. We have sought to clarify how alkaline ammonium salts, released from urea by this enzyme, might alter mucus pH and so affect growth and motility of the bacterium in the gastric mucus environment. METHODS: Experiments were conducted in vitro to determine how the growth and motility of H. pylori are affected by changes in external pH, and how the bacterium, by hydrolysing urea, alters the pH of the bicarbonate buffer that occurs at the gastric mucosal surface. These data were fitted into experimental models that describe how pH varies within the mucus layer in the acid-secreting stomach. RESULTS: H. pylori was motile between pH 5 and 8, with optimal motility at pH 5. It grew between pH 6 and 8, with optimal growth at pH 6. The bacterium had urease activity between pH 2.7 and 7.4, as evidenced by pH rises in bicarbonate-buffered solutions of urea. Changes in buffer pH were dependent upon initial pH and urea concentration, with the greatest rate of pH change occurring at pH 3. Modelling experiments utilizing these data indicated that (1) in the absence of urease, H. pylori growth and motility in the mucus layer would be restricted severely by low mucus pH in the acid-secreting stomach, and (2) urease will sometimes inhibit H. pylori growth and motility in the mucus layer by elevating the pH of the mucus environment above pH 8. CONCLUSIONS: Urease is essential to the growth and motility of H. pylori in the mucus layer in the acid-secreting stomach, but, paradoxically, sometimes it might suppress colonization by raising the mucus pH above 8. This latter effect may protect the bacteria from the adverse consequences of overpopulation.

Bicarbonates↗
PubMed2006

Mucus and MUC in asthma.

PURPOSE OF REVIEW: Asthma is characterized by chronic airway inflammation and a mucus hypersecretory phenotype comprising excess mucus secretion, goblet cell hyperplasia and submucosal gland hypertrophy. This augmented mucus secretion has been relatively undervalued in asthma compared with airway inflammation. However, mucus plugging contributes to airflow limitation and airway hyperresponsiveness, and to morbidity and mortality in asthma. We review recent contributions to this field and therapeutic avenues to control mucus hypersecretion. RECENT FINDINGS: A distinct mucus hypersecretory phenotype may present in asthma. Overexpression of MUC5AC, MUC5B and MUC2 have been described in asthma secretions, but identification of defined biochemical abnormalities and polymorphisms of mucin genes linked to asthma remains elusive. Activation of epidermal growth factor receptor (EGFR) activation appears central in transducing many different stimuli, including oxidative stress, proteases and cytokines. In contrast, nitrosative stress has barely been investigated. The existence of crosstalk between EGFR and other receptor systems may provide new clues regarding the activity of acetylcholine, adenosine and other agonists of G-protein-coupled receptors and other receptor families on mucin secretion. Modern techniques for noninvasive detection of mucus pathology will advance clinical research in this field. SUMMARY: Airway mucus hypersecretion as a part of airway remodelling represents a problem in asthma, and studies of pathophysiology and therapeutic approaches are therefore warranted. Identification of targets such as the EGFR cascade, which are crucial in excessive and abnormal mucus secretion, may lead to the rational design of new antihypersecretory drugs that may enhance future asthma treatment.

Asthma↗
PubMed1996

Colonization by lactobacilli of piglet small intestinal mucus.

The colonization potential of lactobacilli was investigated using small intestinal mucus extracts from 35-d-old pigs. Mucus-secreting tissue from the small intestine of piglets was gently rinsed to remove contents and then shaken in buffer to release mucus from the surface. Numbers of lactobacilli in different portions of the small intestine of 35-d-old pigs were enumerated. Also, mucus isolated from the small intestine of pigs was investigated for its capacity to support the growth of lactobacilli. Results indicated that Lactobacillus spp. inhabit the mucus layer of the small intestine and can grow and adhere to ileal mucus. From adhesion studies of Lactobacillus fermentum 104R to mucus analysed by Scatchard plot, it is suggested that an associating system showing positive cooperativity is involved. Proteinaceous compounds(s) involved in the adhesion to mucus were detected in the spent culture fluid from the growth of strain 104R. Studies are continuing in order to identify and characterize the adhesion-promoting protein(s). From the data, it is proposed that lactobacilli colonize the mucus layer of the small intestine of pigs.

Animals↗
PubMed1990

The adherent gastric mucus gel barrier in man and changes in peptic ulceration.

The mucus barrier is a layer of water-insoluble gel adherent to the gastroduodenal epithelium. In man most previous studies have focused on luminal mucus or histological assessment of presecreted, intracellular mucus--neither of which can be directly correlated with the protective capacity of the adherent mucus barrier. We here describe direct observation of adherent mucus thickness in man, and changes in peptic ulceration. Adherent mucus gel on human antral mucosa is a continuous homogeneous layer of variable thickness, in the range 50-450 microns (median 180 microns), comprising 67% polymeric mucin. In gastric ulcer patients, adherent antral mucus is significantly increased in thickness (median 240 microns), but is very heterogeneous and structurally a substantially weaker gel, comprising only 35% polymeric mucin. Adherent antral mucus from duodenal ulcer patients is homogeneous, significantly thinner (median 110 microns), and structurally a weaker gel, comprising 50% polymeric mucin. The adherent mucus layer from patients with gastric carcinoma resembled that from subjects with gastric ulcer in that it was very heterogeneous, of significantly increased thickness (median 240 microns) and structurally a very weak gel (23% polymeric mucin). These results are discussed in the context of gastroduodenal mucosal protection against acid and pepsin in the gastric juice.

Duodenal Ulcer↗
PubMed1992

Affinity for porcine respiratory tract mucus is found in some isolates of Actinobacillus pleuropneumoniae.

The ability of 17 Actinobacillus pleuropneumoniae isolates representing serotypes 1, 2, 5, and 7, to adhere in vitro to porcine respiratory tract mucus was examined. Adherence of bacteria to crude mucus preparations was evaluated by use of a dot-blot assay and an enzyme immunoassay. Seventy per cent (12/17) of the isolates of A. pleuropneumoniae had affinity, to various degrees, for porcine respiratory tract mucus. No relationship was found between affinity for respiratory mucus and serotype, haemagglutination, lipopolysaccharide (LPS) profiles, or adherence to porcine tracheal rings. However, a correlation was found between affinity for respiratory mucus and capsular material thickness; heavily encapsulated isolated showed no or less affinity for mucus than isolates with a thinner layer of capsular material. Moreover, two encapsulated isolates showed less affinity for mucus than their acapsulated variant. Finally, the affinity of A. pleuropneumoniae for respiratory mucus was heat- and proteinase-K-resistant. Our data suggest that capsular material of A. pleuropneumoniae could mask a surface component, possibly LPS, which has affinity for porcine respiratory mucus.

Actinobacillus Infections↗
PubMed1996

Interleukins-6 and -8 levels in sera and cervical mucus of fertile, idiopathic infertile, and immunoinfertile women: implication in infertility.

PROBLEM: The purpose of this study was to investigate the levels of interleukin-6 and -8 (IL-6 and IL-8) in sera and cervical mucus of infertile (idiopathic and immunoinfertile) women and to compare the levels with those in age-matched normally cycling fertile women. METHODS: Levels of IL-6 and IL-8 were measured in the sera and cervical mucus of fertile and infertile women by the enzyme-linked immunosorbent assay (ELISA). A non-parametric Mann-Whitney test was used to evaluate significance between the means. Linear regression analysis of IL-6 and IL-8 concentrations in serum versus cervical mucus and with antisperm antibody titers was performed by condition as well as all groups together. P < 0.05 was considered significant. RESULTS: Both IL-6 and IL-8 were detected in sera and cervical mucus of fertile as well as infertile groups. Although serum levels of IL-6 and IL-8 were significantly different between fertile and infertile groups, the differences were more pronounced in the cervical mucus samples. Cervical mucus of idiopathic and immunoinfertile women demonstrated significantly (P = 0.002 to < 0.0001) greater concentrations of IL-6 and IL-8 compared to fertile controls. In general, there was no significant correlation between the serum and cervical mucus IL-6 and IL-8 levels, whether analyzed by condition or all groups together. CONCLUSIONS: Elevated levels of IL-6 and IL-8 in cervical mucus of infertile groups may play a role in etiology of idiopathic and immunologic infertility. These findings suggest that the measurements of cytokines (especially IL-6 and IL-8) in cervical mucus may provide a tool for specific diagnosis and possibly treatment of infertility, especially idiopathic infertility.

Antibodies↗
PubMed2006

Comparative study of the intestinal mucus barrier in normal and inflamed colon.

AIM: To study the role of mucus in the spatial separation of intestinal bacteria from mucosa. PATIENTS AND METHODS: Mucus barrier characteristics were evaluated using histological material obtained by biopsy from purged colon, colon prepared with enema and material from untreated appendices fixed with non-aqueous Carnoy solution. Bacteria were evaluated using fluorescence in situ hybridization, with bacterial 16S RNA probes and related to the periodic acid Schiff alcian blue stain. Biopsies from controls (n = 20), patients with self-limiting colitis (SLC; n = 20), ulcerative colitis (n = 20) and 60 randomly selected appendices were investigated. RESULTS: The mucosal surface beneath the mucus layer was free of bacteria in > or =80% of the normal appendices and biopsies from controls. The thickness of the mucus layer and its spread decreased with increasing severity of the inflammation; the epithelial surface showed bacterial adherence, epithelial tissue defects and deep mucosal infiltration with bacteria and leucocytes. Bacteria and leucocytes were found within mucus in all biopsy specimens from patients with ulcerative colitis, SLC, and acute appendicitis. The concentration of bacteria within mucus was inversely correlated to the numbers of leucocytes. CONCLUSIONS: The large bowel mucus layer effectively prevents contact between the highly concentrated luminal bacteria and the epithelial cells in all parts of the normal colon. Colonic inflammation is always accompanied by breaks in the mucus barrier. Although the inflammatory response gradually reduces the number of bacteria in mucus and faeces, the inflammation itself is not capable of preventing bacterial migration, adherence to and invasion of the mucosa.

Acute Disease↗
PubMed1981

Experimental analysis of hydrogen ion diffusion in gastrointestinal mucus glycoprotein.

Experiments were undertaken to test the hypothesis that mucus glycoproteins retard the diffusion of hydrogen ions, a possible protective action of gastric mucus. Mucus and mucus glycoproteins (visible mucus, crude mucin, mucus glycoprotein fractions) were evaluated in two devices designed for this test, a linear diffusion chamber and a hydrogen ion flux chamber. The linear diffusion chamber assessed ion diffusion from a point source through mucus glycoproteins to a H+ detector. A mathematical model of diffusion, based on Fick's law, was adapted to characterize diffusion in this chamber. The H+ flux chamber assessed H+ flux rates across a steep concentration gradient through controlled amounts of mucus glycoprotein. With the exception of human sulfomucin, tested only at dilute concentrations and only in the flux chamber, both procedures indicated that mucosubstances retarded, in a dose-related manner, diffusion of hydrogen ions. Experiments on buffering by crude porcine gastric mucin did not demonstrate significant buffering under physiological conditions. Thus, the present experimental data, the principles of which should be extrapolative to the mucous barrier at the biological level, suggest that mucus glycoproteins can in fact inhibit the diffusion of hydrogen ions.

Animals↗
PubMed1997

Gastric mucus of the guinea pig: proton carrier and diffusion barrier.

Proton transport with the gastric mucus was investigated in the guinea pig in vitro by use of three experimental series. In series I, pH profiles were obtained in the mucus and mucosa of a gastric explant with fine-tipped double-barreled microelectrodes. With a luminal pH of 1.8, pH increased across this layer to approximately 6 at the epithelial surface. Thickness of the gastric mucous gel layer increased continuously by 170 +/- 100 microns/h in the unstimulated and by 450 +/- 120 microns/h in the histamine-stimulated preparation (means +/- SD). In series II, fresh guinea pig gastric mucus was obtained from the gastric mucosa and titrated at 10 degrees C from pH 6.5 to 0.7, followed by an incubation period of 30 min at 37 degrees C. During this incubation period, a spontaneous acidic shift was observed, corresponding to a proton release from the mucus of 130 +/- 19 mM. This proton release could be blocked by the pepsin inhibitor pepstatin and was not observed when titrating down to only pH 3. Buffer values calculated as the mean slope of the titration curves in the pH range of 7 to 3 averaged 40 mM/pH unit. In series III, when titration was repeated with purified porcine mucin, no proton release was observed during incubation at pH 1.0, unless pepsinogen (375 U/ml) had been added before titration. Proton release during incubation at pH 1.0 and 37 degrees C in the presence of pepsinogen averaged 50 mM. The data suggest that protons secreted by the gastric mucosa are buffered by the continuously secreted mucus and transported, bound to the proteins of the mucus, toward the gastric lumen. During this transport, pepsinogen is converted within the mucus to pepsin. Pepsin modifies the buffering properties of the mucus, whereby protons are released from the protein binding. Thus the mucus forms a vehicle for proton transport toward the gastric lumen while, at the same time, constituting a diffusion barrier to prevent proton backdiffusion toward the gastric epithelium.

Animals↗
PubMed1985

Aerosol deposition in the airway model with excessive mucus secretions.

Aerosol deposition in the airways with excessive mucus secretions was investigated utilizing an in vitro airway model lined with various mucus simulants of differing rheological properties. The airway model was made with a straight glass tube (1.0 cm ID and 20 cm in length) and positioned vertically. The mucus simulants were supplied into the tube at a constant rate and made to move upward through the tube as a thin layer (0.6-1.7 mm) undergoing a random wave motion by means of upward airflow. Aerosols (3.0 and 5.0-micron diam) were passed through the mucus-lined tube at flow rates of 0.33-1.17 l/s, and the deposition of the aerosols in the tube was determined by sampling the aerosols at the inlet and the outlet of the tube on filters. During the sampling, pressure drop across the tube model was also measured. Deposition efficiency in the 20-cm-long mucus-lined tube ranged from 13 to 92% with 3.0-micron-diam particles and from 66 to 98% with 5.0-micron-diam particles. This deposition was 25-300 times higher than that in the dry tube. The deposition was higher with increasing viscosity of mucus but was lower with increasing elasticity of mucus. Pressure drop across the mucus-lined tube was much higher than that in the dry tube, and the increase was more prominent with mucous layers with higher viscosity but lower elasticity values. Therefore, aerosol deposition showed a good positive relationship with pressure drop. However, percent increase of aerosol deposition in the mucus-lined tube was 2-5 times higher than that of pressure drop.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗