Mucus rheological properties

Holma, B. (1985). Influence of buffer capacity and pH-dependent rheological properties of respiratory mucus on health effects due to acidic pollution. Set. Total Environ. 41, 101-123. 

GP Martin, C Marriott, I Kellaway. (1976). The effect of natural surfactants on the rheological properties of mucus. J Pharm Pharmacol 28 76P. 

Chronic diseases include cystic fibrosis in which nasal mucus is thick and viscous as a result of abnormal chloride transport across the membrane of the epithelial cells, leading to reduced water secretion. Similarly, chronic sinusitis also reduces nasal mucociliary clearance due to an increase in the rheological properties of mucus. 

It is widely held that mucus should possess specific rheological properties for clearance from the airway to occur. Any alteration in mucus rheology that compromises clearance can predispose the individual to airway disease and infection. Some agents capable of altering mucus rheology are listed in Table 9.2. In addition, the state of mucus hydration (or mucin concentration) will affect the properties of the gel. In... 

Table 9.2 Agents capable of altering the rheological properties of mucus...

Vigil, P. Perez, A. Neira, J. Morales, P. Post-partum cervical mucus biological and rheological properties. Human Reprod. 1991, 6, 475 79. 

Bhat PG, Flanagan DR, Donovan MD. Drug diffusion through cystic fibrotic mucus steady-state permeation, rheologic properties, and glycoprotein morphology. J Pharm Sci 1996, 85, 624-630. 

ADHATODA The leaves of Adhatoda vasica, Nees, family Acanthaceae, are used in India. The constituents include the alkaloid vasicine (peganine), which has a mucolytic effect, i.e. lowers the viscosity of the bronchial mucus by depolymerisation and makes it more liquid, so that it can be transported. The mucocilliary transport of mucous to the periphery depends on the mucous having certain rheological properties. The drug is used as mucolytic in cough mixtures in the form of a liquid extract. 

The rheological properties of bronchietl mucus w is investigated from patients with cystic fibrosis (CF) 6ts well 6ts from normcd patients. 

Mucins are the major structural components of mucus, a thick gelatinous fluid secreted by specialized epithelial cells such as goblet cells that covers and protects many human organs. Mucins are responsible for the rheological properties of mucus and are very high molecular weight... 

The enzymic removal of sialic acid from bovine cervical mucus has been used in an attempt to establish a molecular basis for the rheological properties. The storage modulus, viscosity, and c.d. spectrum were essentially unchanged, indicating that the removal of terminal sialic acid residues does not affect the physical structure of the glycoprotein to any appreciable extent. 

The relation between the viscosity and elasticity of the secretions is one of the determining factors in transport velocity. If the gel phase is in practice the only one really transported, the sol phase creates a low-resistance milieu where the cilia can beat, an environment that is essential for transport in the direction of the upper airways. One of the most important rheological properties of mucus is viscosity. Viscosity is resistance to flow and represents the capacity of a material to absorb energy while it moves. Elasticity is the capacity to store the energy used to move or deform material. The ratio between viscosity and elasticity appears to be an important determinant of the transport rate (6,10). Mucus transport by ciliary beating is influenced by the viscoelastic and surface properties of the mucus. Theoretical models suggest that a decrease in the ratio of viscosity to elasticity can result in an increase in mucociliary transport (13). 

King M, Macklem PT. Rheological properties of microliter quantities of normal mucus. J Appl Physiol 1977 42 797-802. 

The surfactant film at the air-mucus interface is probably important for the rheological properties of the extracellular layer by stabilizing the aqueous layer mechanically and by reducing the evaporation of water (54,93). These are well-known functions of surfactant films if spread on top of a water surfaee (94). Fluid balance in the airway lining layer may also be influenced by the recently demonstrated effeet of surfactant in stimulating chloride secretion by airway epithelial cells (95). 

The coordination of cilia motility is controlled by neural innervation, chemical pacemaking, and hormonal stimulation, and the effects of ions such as calcium and potassium. Cilia beat in a coordinated fashion to achieve the unidirectional propulsion of mucus with the frequency of the ciliary beat, which is dependent upon the environment. Human nasal cilia have been reported to beat, in vitro, with an average frequency of 10 Hz. Any rheological abnormalities in the mucus gel, particularly those that alter the elastic properties of mucus, can greatly affect clearance and undermine ciliary activity in the nasal cavity. In such circumstances, the adhesiveness of the mucus layer may allow it to remain in contact with the underlying cell layers and retain any substances introduced into the nasal cavity. 

J. M. Zahm, S. Girod de Bentzmann, E. Deneuville, C. Perrot-Minot, A. Dabadie, F. Pennaforte, M. Roussey, S. Shak, and E. Puchelle. Dose-dependent in vitro effect of recombinant human DNase on rheological and transport properties of cystic fibrosis respiratory mucus. Eur. Respir. J. 8 381-386 (1995). 

M. King, J. M. Zahm, D. Pierrot, S. Vaquez-Girod, and E. Puchelle. The role of mucus gel viscosity, spinnability and adhesive properties in clearance by simulated cough. Bio rheology 26 737-745 (1989). 

In asthmatic patients, the most common symptoms are dyspnea and bronchospasm than can usually be reversed with bronchodilatation therapy that probably has no effect on mucus clearance transport (20). Hypersecretion is usually present in the acute episodes of asthma and normally mucus transport is impaired due to reduction of ciliary activity (21). Mucus hypersecretion and changes in the rheological or surface properties of mucus may also cause reduction of ciliary activity (6). In these patients, mucus transport can be recovered or remain reduced, despite favorable changes in mucus viscoelasticity after an exacerbation. 

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