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Biomedical subjects

J M Zahm

Publications and source records attributed to J M Zahm.

At least 19 recordsLinked to original sources
PubMed1992

Phospholipid composition and surface-active properties of tracheobronchial secretions from patients with cystic fibrosis and chronic obstructive pulmonary diseases.

Among the various components of tracheobronchial secretions, lipids and particularly phospholipids have been shown to influence rheological properties of airway secretions in patients with cystic fibrosis. We studied the phospholipid composition of tracheobronchial secretions, collected from patients suffering from cystic fibrosis (CF) and other chronic obstructive pulmonary diseases (COPD), and we analyzed the possible relationship between the phospholipid profile and the wettability of tracheobronchial secretions evaluated by the measurement of contact angle. Although total phospholipid content and contact angle of tracheobronchial secretions were significantly increased (P less than 0.01) in CF compared to COPD, no significant relationship existed between these two parameters. The concentrations of the different phospholipid subclasses were not homogeneously modified according to the origin of the secretions. Compared to COPD secretions, the CF secretions were characterized by a significant (P less than 0.001) increase in rigidifying fractions such as sphingomyelin and phosphatidylserine/phosphatidylinositol and a significant (P less than 0.001) decrease in surface-active fractions, such as phosphatidylcholine and phosphatidylglycerol (PG) (P less than 0.001). In the two groups, the surface-active phospholipid fraction, PG, was negatively correlated to the contact angle of tracheobronchial secretions. These results suggest that a decrease in PG content in CF secretions may be one factor responsible for an increase in their adhesivity to the respiratory mucosa, and, consequently, for mucus stasis and severity of bronchial obstruction in cystic fibrosis.

Adolescent↗
PubMed1992

Pseudomonas aeruginosa adhesion to normal and injured respiratory mucosa.

Human nasal polyps in outgrowth culture were used to study the adhesion of Pseudomonas aeruginosa to respiratory cells. By transmission electron microscopy, bacteria associated with ciliated cells were identified trapped at the extremities of cilia, usually as aggregates of several bacterial cells. They were never seen at the interciliary spaces or attached along cilia. Bacteria were also seen to adhere avidly to migrating cells of the periphery of the outgrowth culture. Using a model of repair of wounded respiratory epithelial cells in culture, we observed that the adhesion of P. aeruginosa to migrating cells of the edges of the repairing wounds was significantly higher than the adhesion to non-migrating cells and that adherent bacteria were surrounded by a fibronectin-containing fibrillar material. The secretion of extracellular matrix components is involved in the process of epithelium repair following injury. To investigate the molecular basis of P. aeruginosa adhesion to migrating cells, bacteria were treated with a fibronectin solution before their incubation with the respiratory cells. P. aeruginosa treatment by fibronectin significantly increased their adhesion to migrating cells. Accordingly, we hypothesize that during cell migration, fibronectin secreted by epithelial cells may favour P. aeruginosa adhesion by establishing a bridge between the bacteria and the epithelial cell receptors. Such a mechanism may represent a critical step for P. aeruginosa infection of healing injured epithelium.

Bacterial Adhesion↗
PubMed1992

Role of the physiochemical properties of mucus in the protection of the respiratory epithelium.

The respiratory mucus is a very complex biological material, which possesses both flow and deformation rheological properties, characterized by non-linear and time-dependent viscoelasticity and physical properties of adhesiveness and wettability. Viscosity and elasticity are directly involved in the transport capacity of mucus, whereas wettability and adhesiveness contribute to the optimal interface properties between the mucus and the epithelial surface. Optimal conditions for the protective and lubricant properties of respiratory mucus are represented by high wettability, and adhesiveness high enough not to induce flow of mucus in the respiratory bronchioles under gravity but low enough to mobilize mucus by airflow during coughing. An intermediate viscoelasticity is also required for an optimal mucociliary transport. Different biochemical constituents such as glycoproteins, proteins, proteoglycans and lipids are involved in the gel properties of respiratory mucus. During bronchial infection and particularly in cystic fibrosis, the loss of water and the increase in macromolecules result in a marked increase in viscosity and adhesiveness responsible for the mucus transport impairment. The various lipids present in mucus contribute differently to the physicochemical properties. Surface-active phospholipids, such as phosphatidylcholine and phosphatidylglycerol improve the wettability of mucus, whereas neutral lipids and glycosphyngolipids contribute to the hyperviscosity of mucus during infection. Phospholipids and associated mucins are also implicated in the interaction between bacteria and epithelial cells. Therefore, the respiratory mucus needs appropriate physicochemical properties for the protection, hydration and lubrication of the underlying airway epithelium.

Adhesiveness↗
PubMed1991

Proliferation, differentiation and ciliary beating of human respiratory ciliated cells in primary culture.

The growth, differentiation, ciliary beating pattern and frequency of human respiratory ciliated cells in primary culture were studied by scanning and transmission electron microscopy and by videomicroscopy. The epithelial cells were obtained as outgrowth from explants of adult nasal polyps. When the explants were grown on type-I and type-IV collagen substrates in a standard serum-free, hormone-supplemented medium, a high percentage of ciliated cells (range 29 +/- 5% to 37 +/- 6%) was present within 2 days of culture. After 5 days of culture, the percentage of ciliated cells near the explant was 51 +/- 5%. Most of the cultured ciliated cells (85%) were characterized by individual cilia showing a coordinated movement during the beat cycle and a beating frequency (13.3 +/- 1.3 Hz) similar to that reported in vivo. In the other 15% of the ciliated cells, the dyskinetic cilia were aggregated into clumps and characterized by a rigid and planar bending movement and a lower (P less than 0.01) beating frequency (10.7 +/- 1.4 Hz). It is suggested that the latter type of cell, already described during fetal development, might be an intermediate type of ciliated cell which appears temporarily during the surface respiratory epithelial differentiation.

Cell Differentiation↗
PubMed1991

Three-dimensional imaging of the mucus secretory process in the cryofixed frog respiratory epithelium.

Using the frog palate as a representative model of human mucociliary epithelium, we analyzed, after quick freezing fixation, the three-dimensional (3-D) respiratory mucus secretory release with high voltage (200-300 kV) transmission electron microscopy (TEM). The 3-D vision of the mucus release from the secretory cells was obtained as stereo-pairs and "bas-relief" images after analysis of stereo-pairs using an image analyzer. After standard glutaraldehyde fixation, the secretory cells showed a typical goblet shape with secretory granules heterogeneous in size and electron-density which often fuse together. On the other hand, quick-frozen secretory cells exhibited a columnar shape and their membrane-bound secretory granules contained a homogeneously dark matrix. The expanded gel mucus layer was preserved and its depth never exceeded 2 microns. When the epithelium was immersed in culture medium in presence of cholinergic agonist, a marked discharge of mucus was observed and the granules swelled at the apex of the secretory cell before being discharged in the lumen. In native cryofixed epithelium, the secretory granules exhibited a marked deformability during the process of their extrusion from the secretory cell. Clusters of secretory granules surrounded by cytoplasmic material were observed in the extracellular lumen, suggesting an apocrine-type secretion. These observations indicate that rapid cryofixation and 3-D stereoscopic imaging enable a unique opportunity to analyze, without artifact, the mucous secretory process. We speculate that, apart from the classical merocrine-type secretion mechanism, the respiratory mucus may be released, at least partly by an apocrine-type secretion.

Animals↗
PubMed1991

Role of phospholipid lining on respiratory mucus clearance by cough.

Phospholipid lining, present at the respiratory mucus-mucosa interface, may have an important role in the protective function of the airways by its abhesive properties and may also facilitate mucus transport. To mimic respiratory mucus-mucosa interface, monolayers of three different forms of phosphatidylglycerol (PG) have been deposited on glass slides by the Langmuir-Blodgett technique. Mucus adhesion and clearance by cough of mucus on these PG-coated or noncoated surfaces have been analyzed and compared, using frog respiratory mucus as "normal" mucus. Among the three PG types studied, the phosphatidylglycerol distearoyl, which is the phospholipid with the longest saturated fatty acid chain, was found to significantly improve the mucus cough clearance by decreasing the mucus work of adhesion compared with the noncoated surfaces. On the other hand, phosphatidylglycerol dipalmitoyl did not improve mucus cough clearance although it decreased mucus adhesion, and phosphatidylglycerol dioleyl did not improve either mucus cough clearance or mucus adhesion.

Animals↗
PubMed1991

Wound repair of human surface respiratory epithelium.

Surface airway epithelium is frequently injured by noxious inhaled agents, epithelial wound repair may be an important process by which the epithelial barrier integrity is maintained. To evaluate the role of surface airway cells in the wound repair process, we developed an in vitro wounding model of human nasal epithelial respiratory cells in primary culture. Circular wounds were made in the epithelial cell culture by detaching, with a glass capillary, approximately 50 cells from the collagen matrix. Video microscopy and electron microscopy observations demonstrated the contribution of two main events during the repair process: the spreading of the cells at the edge of the wounded surface, and the migration of epithelial cell sheets. Complete wound closure occurred within 5 to 8 h. The inhibition of wound repair by cytoskeleton inhibitors or cellular protein synthesis inhibitors suggested that these factors are involved in the wound repair process of surface airway epithelium.

Actin Cytoskeleton↗
PubMed1991

Differential adhesion of Pseudomonas aeruginosa to human respiratory epithelial cells in primary culture.

Human nasal polyps in outgrowth culture were used to study the Pseudomonas aeruginosa adhesion to respiratory cells. By scanning electron microscopy, P. aeruginosa were seen associated with ciliated cells, but by transmission electron microscopy, bacteria were never seen at the interciliary spaces or attached along cilia, but were identified trapped at the extremities of cilia, usually as bacterial aggregates. A fibronectin-containing fibrillar material was seen associated with aggregated bacteria. By time-lapse video microscopy, bacteria were seen to aggregate in the culture medium following their addition to the culture wells. Progressively, these aggregates were trapped by cilia or attached to migrating cells of a lower cell layer that protruded beneath the upper layer cells, at the outgrowth periphery. P. aeruginosa adhesion to these lower cell layer migrating cells was significantly higher than to ciliated or nonciliated cells of the upper cell layer. Migrating cells were intensely labeled by the complexes Con A and arachis hypogea agglutinin (PNA)-FITC, in contrast to the other cells. The percentage of PNA-labeled cells with attached bacteria was significantly higher than that without bacteria. These results suggest that changes of cell surface glycoconjugates related with cell migration may favor P. aeruginosa adhesion to respiratory cells.

Bacterial Adhesion↗
PubMed1991

Role of simulated repetitive coughing in mucus clearance.

The role of repetitive simulated coughing on the clearance of gel mucus simulant was investigated in vitro, by using a simulated cough machine. The repetition of cough induced a significant increase (p less than 0.01) in mucus simulant clearance (139.3 +/- 78.7 mm) in comparison to a single cough (24.9 +/- 27.5 mm). Moreover, the increase in frequency of the repetitive coughing induced a marked and significant increase in mucus simulant clearance (75.4 +/- 51.1 mm and 139.3 +/- 78.7 mm at 0.1 Hz and 1.6 Hz frequency, respectively). A significant (p less than 0.05) correlation was observed between the percentage increase of clearance and both shear-thinning index (r = 0.62) and the thixotropic index (r = 0.63). These results suggest that the shear-dependent properties of mucus, associated with a repetitive coughing, may increase the efficiency of mucus clearance by air flow mechanisms.

Cough↗
PubMed1990

Quantitation of in vitro ciliated cell growth through image analysis.

Ciliated cell cultures can be produced in outgrowths from explants of human respiratory epithelium. An image analysis technique was developed to quantify the percentage of active ciliated cells present in these cultures. The subtraction 2 by 2 of five successive video images of the cultures, followed by the addition of the resulting images, allowed the determination of the culture surface covered by ciliated cells. The percentage of this surface varied according to the region of the explant (27.7% in the outgrowth near the explant and 4.1% at the periphery of the outgrowth). High variations were observed within the same region of an outgrowth, as well as from one outgrowth to another. However, maximal differentiation was observed after 4 d of culture. The quantitation technique described in the present work might be useful for studying in vitro the respiratory epithelial injury and the subsequent repair processes.

Cell Membrane↗
PubMed1990

Functional activity of ciliated outgrowths from cultured human nasal and tracheal epithelia.

Primary cultures of respiratory epithelium were produced as outgrowths from human fetal and adult tracheal and nasal polyp explants. Video recordings of the epithelial cell outgrowths were carried out after 5 days of culture and the ciliary beating frequency was analyzed by using a video technique. Uniform fields of differentiated ciliated cells were observed near the edge of the explant. In the transition region of the outgrowth from the explant to the outgrowth periphery, isolated ciliated cells were present, as well as cells with fused cilia. The ciliary beating frequency of the outgrowth of well-differentiated ciliated cells (13.5 +/- 1.4 Hz) was significantly higher (p less than 0.001) than the beating frequency of both the explant (11.9 +/- 0.7 Hz) and the ciliated cells with fused cilia (9.8 +/- 1.7 Hz). The same differentiation stages and functional activities were observed in the outgrowth cultures, whatever their origin. These in vitro models are comparable with each other and therefore could be useful for studying the ciliogenesis and functional activity of the human respiratory epithelium.

Cilia↗
PubMed1989

Role of mucus and cilia in nasal mucociliary clearance in healthy subjects.

Large interindividual variations of nasal mucocilliary clearance across healthy subjects have been previously described. The aim of this study was to evaluate the respective role of the nasal mucus quality and ciliary activity in determining nasal mucociliary clearance and to study changes in these variables across time and with environmental conditions. In 20 healthy nonsmoking volunteers, the in vivo nasal mucociliary clearance was measured with the saccharin test. Then, nasal mucus and ciliated cells were collected. The in vitro ciliary beat frequency of the nasal cells was evaluated by a photometric analysis. The in vitro nasal mucus transport rate was evaluated by use of the frog depleted-palate model. The nasal mucociliary transport time (NMTT) of saccharin was greater than 30 min in seven subjects and was 13.6 +/- 6.1 min (mean +/- SD) in the remaining 13 subjects. NMTT was correlated to the in vitro transport rate of the nasal mucus (r = -0.75, p less than 0.001), but not to the ciliary beating frequency or to ambient temperature, relative humidity, or air pollution indices measured. Moreover, large intraindividual variations of NMTT, measured on two occasions 4 to 8 wk apart, were found to be significantly correlated with changes in mucus transport rate (r = -0.60, p less than 0.05).

Adult↗
PubMed1989

Effect of air humidity on spinability and transport capacity of canine airway secretions.

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T degrees:20 degrees C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m3 air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m3 air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p less than 0.01) lower (range: 0.59-0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70-1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p less than 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.

Air↗
PubMed1989

The role of mucus gel viscosity, spinnability, and adhesive properties in clearance by simulated cough.

We investigated the role of the viscoelastic and adhesive properties of mucus gel simulants on the clearance of mucus by simulated cough. Mucus-like gels with widely varying viscoelastic properties were prepared from polysaccharides crosslinked with sodium borate. Cough was simulated by opening a solenoid valve connecting a model trachea to a pressurized tank. The clearance of gels lining the model trachea was quantified by observing marker particle transport. Viscosity elastic modulus, relaxation time and yield stress were measured with a steady-shear viscoelastometer. Spinnability (thread formation) was determined with a filancemeter. Adhesivity (surface tension) was measured by the platinum ring technique. The viscoelastic and adhesive properties of the mucus gel simulants spanned the ranges observed for bronchial secretions from patients with COPD. The relationship between simulated cough clearance and the viscoelastic and adhesive properties of the gels was analyzed by stepwise linear regression of the non-zero data matrix. The major independent variable relating to clearance was viscosity. Secondary, but highly significant dependences, were also found for spinnability and adhesivity. Elastic modulus, relaxation time and yield stress had no independent effect on cough clearance over the investigated range. The results indicate that, in the absence of airway surface liquid, cough-type clearance relates primarily with mucus gel viscosity. For a given viscosity, clearance is also impaired by spinnability, i.e. the capacity of the mucus to form threads. At constant viscosity and spinnability, clearance is further impaired by an increase in the adhesivity of the mucus. The negative dependence of each of these physical factors can be rationalized in terms of their inhibitory effect on wave formation in the mucus lining layer during high velocity airflow interaction.

Adhesiveness↗
PubMed1989

The role of mucus sol phase in clearance by simulated cough.

Using a simulated cough machine, we analyzed the effect of adding tensio-active liquids as sol phase simulant on the clearance of gel mucus simulant by cough. Polysaccharides crosslinked with sodium tetraborate were used at different concentration as gel mucus simulant. A drop of gel mucus simulant was deposited either directly on the model trachea or on a sol phase layer simulant (2% sodium dodecyl sulfate in water). The clearance of the mucus simulants was quantified by observing the movement of marker particles in the gel layer. The viscoelastic properties of gel mucus simulants were determined by using a viscoelastometer (SEFAM). The adhesive properties were analyzed by means of the platinum ring technique. The wettability of the mucus simulants was quantified by the automatic measurement of the contact angle of the drop of gel on the model trachea. We found that the addition of a sol phase significantly decreased by about 50% the adhesivity and wettability of the gel mucus simulants. This decrease was associated with a marked enhancement of cough clearance, whatever the viscoelastic properties of the gel mucus simulants. These results suggest that the sol phase is essential in bronchial respiratory mucus clearance by the cough mechanism.

Adhesiveness↗
PubMed1989

Comparative rheological profile of rat gastric and duodenal gel mucus.

Methods for measuring the adhesiveness, plasticity, viscoelasticity and spinnability of mucus microsamples have been developed. The rheological properties of the rat gastric and duodenal gel mucus have been analyzed and compared. Using a controlled stress rheometer (Carri-Med), flow and creep experiments showed that gastroduodenal mucus exhibits a typically non-newtonian, pseudoplastic and viscoelastic behaviour. The apparent viscosity (7,800 +/- 11,000 Pa.s) and yield stress (24.9 +/- 8.5 Pa) of gastric mucus were significantly higher than the duodenal mucus viscosity (39 +/- 160 Pa.s) and yield stress (12.9 +/- 2 Pa). Spinnability of gastric mucus, measured with a Filancemeter (SEFAM), was significantly lower (4.9 +/- 2.5 mm) in comparison to duodenal mucus (6.9 +/- 1.5 mm). Adhesive properties of gastric mucosa (analyzed with the platinum ring method) were not significantly different in comparison to duodenal mucus (99.9 +/- 31.5 mN/m and 92.8 +/- 11.2 mN/m, respectively).

Adhesiveness↗
PubMed1988

[Methods of studying mucociliary function].

The mucociliary system represents the first respiratory tract barrier which acts by removing insoluble particles from the conductive airways. Impairment of mucociliary clearance, due to respiratory mucus and ciliary activity abnormalities, leads to mucus stasis, responsible for infection and bronchial obstruction. In obstructive airway diseases, the efficiency of the mucociliary function can be investigated quantitatively by in vivo and in vitro tests. In vivo mucociliary clearance can be measured by radioactive marker techniques. In vitro tests can evaluate the physical properties and transportability of mucus. The ciliary function can easily be analyzed on ciliated cells collected by nasal or bronchial brushing. Coupled with respiratory function tests, the investigation of the mucociliary function by in vivo and in vitro tests, provides a guideline for selection and assessment of drugs used to correct mucociliary disorders.

Bronchi↗