Accumulation of mucus

Clearance in the upper, or ciliated, region is governed by the rate of mucus transport along the airways. These rates have been measured in the human nose and in dogs, rats, and other species. Asmundsson and Kilbum, Hilding, and Iravani established that mucociliary clearance rates increase from the distal bronchi toward the trachea. Because bronchial openings retard mucus flow, bifurcations receive an accumulation of mucus and associated particles. The rate of mucus production and mucus thickness and velocity vary from one person to another. Thickness increases and velocity decreases greatly when some toxic elements are present in the airway. 

Lobelia inflata has for many years been one of the most widely discussed and hotly debated articles used in medicine. While many herbalists contend that it is the most valuable of all botanic remedies, official medicine in England classifies it as a poison. Herbalists who use Lobelia insist that it is most certainly not a poison, and that it can be administered by them in large doses with perfect safety. They use it chiefly as an emetic, and, as its administration brings about the prompt removal of accumulations of mucus, the action in bronchial complaints is speedy and beneficial. Coffin s comments in this connection are enthusiastic "Lobelia is decidedly the most certain and efficient emetic known, and is at the same time safe in its operations. Unlike most emetics from the mineral kingdom, it produces its specific effect without corroding the stomach or producing morbid irritation and inflammation of the mucous membrane of this organ, which are so common in the use of antimony, zinc, and the sulphate of copper. Lobelia may emphatically be said to operate in unison with the laws of life. "... 

An example of a disease that results from a deletion mutation is cystic fibrosis. The presence of mutated genes in which three thymine bases are absent produces cells in the lungs that are defective in the transport of molecules such as sodium. A result is the accumulation of mucus in the lungs. Bacteria readily colonize the mucus and become resistant to treatments intended to kill them. As... 

Recently, Cl" channels have been discovered. These channels have no sequence relationship to the voltage-gated Na, and Ca channels. One such channel is involved in the disease, cystic fibrosis. In this disease, regulation of the channel is defective. The altered function of the channel in epithelia causes elevated levels of sodium and chloride ions in sweat and, through unknown processes, the accumulation of mucus in the respiratory tract and failure of exocrine secretion in glands, such as the pancreas. Blockage of airways leads to chronic lung infections that, with other effects of the Cl" transport deficiency, can be fatal. 

Suez, D., and Szefler, S. J. (1986). Excessive accumulation of mucus in children with asthma A potential role for erythromycin A case discussion. J. Allergy Clin. Immunol. 77, 330-334. 

These authors enclosed healthy copies of the human cystic fibrosis membrane conductance regulator (CFTR) gene in liposomes, which were then introduced into the lungs of mice with artificially induced cystic fibrosis (the liposomes fuse with cell membranes so that the healthy DNA passes into the cells). Normal ion transport was restored and the accumulation of mucus was prevented. 

At any point on the bronchial tree, the transport surface is determined by the inside diameter and the number of airways at this level. Moving from the center toward the periphery, diameters decrease, but the number of airways increases exponentially so that the transport surface decreases proportionally. As a result, the transporting surface of the airways decreases from the peripheral to the central airways. Accumulation of mucus in the central airways is normally countered by the higher mucus transport rate centrally than peripherally, and possibly by a greater reabsorption of watery constituents centrally. 

Figure 4.5 Lung morphology from pig lung 24 hours post phosgene exposure (2000 mg min m" ) treated with protective ventilation. Little oedema or inflammatory cell infiltrate was observed (A), with the majority of alveolar spaces (B) showing no evidence of pathology and an open structure comparable to air controls ( ). Small accumulations of mucus and cellular debris (t) were observed in the lumens of a few of the conducting airways (C). Few focal areas of inflammatory cell infiltrate ( ) were observed in the submucosa of the conducting airways (D). Dark scales are 200 pm and white scales are 50 pm. Stippled boxes show the area expanded in the adjacent image.

Three factors contribute to airway obstruction in asthma (1) contraction of the smooth muscle that surrounds the airways (2) excessive secretion of mucus and in some, secretion of thick, tenacious mucus that adheres to the walls of the airways and (3) edema of the respiratory mucosa. Spasm of the bronchial smooth muscle can occur rapidly in response to a provocative stimulus and likewise can be reversed rapidly by drug therapy. In contrast, respiratory mucus accumulation and edema formation are likely to require more time to develop and are only slowly reversible. 

Cystic fibrosis is an autosomal recessive disease caused by mutations of the cystic fibrosis transmerobrane conductance regulator (CFTR) gene producing a dysfunctional chloride channel, normally located on the apical membrane of exocrine glands [16]. The disease manifests itself at an early age in the lung with accumulation of thick, sticky mucus and bacterial infections. These infections are followed by an inflammatory response, resulting in an Infiltration of neutrophils... 

Phaeocystis colonies are considered to be less palatable to copepods than diatoms. This has mainly been attributed to the large size of these colonies. In addition it has been suggested that acrylate may accumulate to high concentrations in the mucus surrounding Phaeocystis colonies (Davidson and Marchant 1987 Guillard and Hellebust 1971). Since acrylate may have antimicrobial properties at elevated concentrations (Sieburth 1960 Slezak et al. 1994), DMSP-lyase could be involved in the accumulation of this compound to prevent microbial attack and grazing. In intact and growing Phaeocystis... 

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