Soluble mucus

Soluble mucus was considered to be the transient physical dissolution product of the visible surface mucin before it undergoes further enzymatic degradation in the stomach (Gll). It precipitates from filter ... 

When 1.5 volumes acetone is added to the trichloroacetic acid filtrate of the gastric juice, an abundant flocculent precipitate forms, which contains all the components of dissolved mucin with the exception of soluble mucus. If this precipitate is taken up in dilute alkali and then acidified with dilute HCl down to pH 3.5, a fine flocculent precipitate forms, which we named dissolved mucoprotein (G27, G36). It was later renamed glandular mucoprotein (G9, G38) because of its close relationship to the fundic glands of the stomach. This material contained much protein its nitrogen content was 12.61 0.44% and its tyrosine content 7.50 0.65% by the Folin-Giocalteu reaction. The reducing substance content was 6.38 1.48% before and 12.5% after hydrolysis (G9, G27, G36) (see Table 4). Werner (W9) determined the composition of this mucoprotein fraction and found that it contained 11.2% N by Kjeldahl, 8.8% hexosamine, 4.8% uronic acid, and 2.0% sialic acid. 

Pugh et al. (P7) and Mack et al. (Mia, M2), using free boundary electrophoresis, showed that mucoprotein and mucoproteose fractions of the dissolved mucin (G5) had different electrophoretic mobilities mucoprotein fast anodic mobility (5.5-6.9 X cm sec volts ), mucoproteose slow anodic mobility (0.5-1.0 X cm sec volts ) in veronal buffer of pH 9.2 (Fig. 1). Soluble mucus had intermediate mobility of — 3.5 X 10 . It was also noted by Mack et al. (Ml) that the mucoprotein fraction processed from the acid human gastric juice, when nm by itself on Tiselius electrophoresis or when added to acid gastric juice, did not have as fast mobility as the fastest anodic component of the gastric juice, which had a mobility of 7.4-7.S X cm sec volts and which probably, as we know now, corresponded to the complex of pepsin and mucoprotein (see G5). 

Thus, Beaumont described visible mucus, but he implied that gastric juice free of visible mucus contains soluble mucus as well. Pure gastric juice, he wrote, is clear, and almost transparent ... similar to the thin mucilage of gum arabic, slightly acidulated with muriatic acid. As for the functions of mucus, Beaumont s mentor in science, Robley Dunglison, wrote that mucus, in liquid state, serves as a protective covering to different parts. Beaumont agreed. 

Lungs also secrete nonvolatile compounds. Lipid-soluble compounds may thus be transported with the alveobronchotracheal mucus to the pharynx, where they are swallowed. They may then be excreted or reabsorbed. Particles are also removed by this mucociliary escalator. 

The upper and lower respiratory tracts respond differently to the presence of toxicants. The upper respiratory tract is affected mostly by toxicants that are water soluble. These materials either react or dissolve in the mucus to form acids and bases. Toxicants in the lower respiratory tract affect the alveoli by physically blocking the transfer of gases (as with insoluble dusts) or reacting with the wall of the alveoli to produce corrosive or toxic substances. Phosgene gas, for example, reacts with the water on the alveoli wall to produce HC1 and carbon monoxide. 

HD vapors are heavier than air and tend to seek lower elevations. HD is slightly soluble in cold water and soluble in most organic solvents. Exposure in any concentration will cause severe choking. Exposure to vapors in low to moderate concentrations will cause temporary blindness and inflammation of the entire respiratory tract. Higher concentrations cause permanent blindness and strip the bronchial tubes of their mucus membrane linings. 

Interaction with the cervical mucus has been anticipated to be highest with cationic species [58], such as benzalkonium chloride, chlorhexidene, and vantocil (polyhexamethylene biguanide). A clear exception is the water-soluble sulfated polystyrene derivative (ORE 13904) [23]. In general, sperm penetration is lower for water-soluble cationic polymers than for anionic or nonionic polymers [59]. 

The major respiratory factors in the control of ozone uptake are the morphology (including the mucus layer), the respiratory flow, the physical and chemical properties of mucus, and the physical and chemical properties of ozone. The next two sections discuss models of the morphology and the air and mucus flow. The physical and chemical properties of bronchial secretions have been reviewed by Barton and Lourenco and Charman et al. The relevant physical and chemical properties of ozone, are its solubility and diffusivity in mucus and water and its reaction-rate constants in water, mucus, and tissue. 

Solubility data for mucus are not available, but Table 7-1 indicates that the Henry s law constant for ozone in water under the conditions of the lung is 9,700. Solubility data for pure ozone and other physical properties are available from various sources. Air Quality Criteria for Photochemical Oxidants reports an ozone solubility of 0.494 ml/ 100 ml of water at 0 C for ozone at 760 mm Hg extrapolation of data from Thorp indicates 1.09 g/liter of water at 0 C and approximately 0.31 g/liter of water at 37 C for 100% ozone. The value for 37 C agrees closely with the solubility calculated from the Henry s law constant for pure ozone at 760 mm Hg. 

A realistic boundary condition must account for the solubility of the gas in the mucus layer. Because ambient and most experimental concentrations of pollutant gases are very low, Henry s law (y Hx) can be used to relate the gas- and liquid-phase concentrations of the pollutant gas at equilibrium. Here y is the partial pressure of the pollutant in the gas phase expressed as a mole fraction at a total pressure of 1 atm x is the mole fraction of absorbed gas in the liquid and H is the Henry s law constant. Gases with high solubilities have low H value. When experimental data for solubility in lung fluid are unavailable, the Henry s law constant for the gas in water at 37 C can be used (see Table 7-1). Gas-absorption experiments in airway models lined with water-saturated filter paper gave results for the general sites of uptake of sulfur dioxide... 

Figure 7-2 illustrates a three-compartment structure assumed by McJilton et al. for describing radial diffusion. It consisted of a gas phase in the lumen of the airway, a liquid layer that lined the airway, and a tissue compartment. The rate of movement of the gas into the liquid layer, dm /dt is a function of the solubility of the gas in the liquid, as defined by the Henry s law constant. The rate of movement of the gas molecules across the liquid layer to the tissue compartment, dm /dt is a function of the diffusion co cient of the gas in the mucus and serous... 

Frank in dogs. The most likely explanation is that the model does not account for chemical reactions of ozone in the mucus and epithelial tissue. Another problem is that the nose is believed to behave more like a scrubbing tower with fresh liquid at each level, inasmuch as the blood supply is not continuous for the entire length of the nose, as assumed in the model. Neglecting the surface area, volume, flow, and thickness of the mucus layer in the nose will probably also give erroneous results for soluble gases with a small diffusion coefficient in mucus and for singlebreath inhalations of a low concentration of any gas. 

Values above 0 indicate the potential for absorption directly across the respiratory tract epithelium. Very hydrophilic substances may be retained within the mucus or for low molecular weight substances (MW < 200), could be absorbed through aqueous pores. Very low water solubility (1 mg/1 or less) and small particle size (below 1 p,m) indicates a potential for accumulation in the lung tissue. 

Mechanism of Action Asulfhydryl compound with similar properties to those of penicillamine and glutathione that undergoes thiol-disulfide exchange with cysteine to form tiopronin-cysteine, a mixed disulfide. This disulfide is water soluble, unlike cysteine, and does not crystallize in the kidneys. May break disulfide bonds present in bronchial secretions and break the mucus complexes. Therapeutic Effect Decreases cysteine excretion. 

Apart from being a diffusional barrier, mucin can also interact with drugs to decrease their bioavailability, as has been shown with tetracycline [106], phenylbutazone, and warfarin [107]. On the other hand, studies in rats showed that binding of some water-soluble drugs to intestinal mucus was essential for their absorption and that damage to the mucus significantly reduced absorption [108], The acidic mucus is essential for lipid absorption and could be important for the diffusion of lipophilic drugs (see below). 

Nakamura, J., et al. 1978. Role of intestinal mucus in the absorption of quinine and water soluble dyes from rat small intestine. Chem Pharm Bull Tokyo) 26 857. 

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