The contribution of added proteins to mucus viscoelasticity [proceedings].
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Biomedical subjects
Publications and source records attributed to C Marriott.
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The solubility of progesterone was determined in several different bile salt-phospholipid mixtures, and it is concluded that: (1) The solubility in unconjugated bile salts is greater than in the conjugated analogues, and the solubility in deoxycholate solutions is twice that in cholate solutions. (2) Substitution of hydroxyl groups in the 11 and 21 positions of progesterone increases solubility, whilst substitution in the 17-position decreases solubility in bile salt solutions. (3) Progesterone solubility in mixed bile salt solutions is proportional to the mole ratio of the surfactant mixture. (4) Sodium deoxycholate (SDC)-phospholipid sols show no such linear solubilizing properties; a minimum occurring at a mole ratio of SDC to phospholipid of 1 : 4. (5) There is a break in the solubility curve of progesterone in lysophosphatidycholine (LPC)/phosphatidylcholine (PC) mixtures at a mole ratio of 65 : 35 coincident with maximum viscosity. (6) Introduction of SDC into LPC/PC mixtures results in decreased progesterone solubility.
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Reflux of duodenal contents into the stomach has been implicated in the disruption of mucosal defence and the subsequent occurrence of gastric ulcer. The change produced in the rheological properties following the addition of bile salts and phospholipids to mucus samples was used to assess resultant structural changes. Sodium deoxycholate, sodium taurodeoxycholate, sodium glycocholate, and lysophosphatidylcholine decreased both viscosity and elasticity, indicating that structural breakdown had occurred, whereas phosphatidylcholine could not be shown to have any effect. It is therefore suggested that some of the ulcerogenic activity of naturally occurring surfactants may be associated with their ability directly to reduce mucus consistency.
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The rheological evaluation of preparations containing 10, 15, 20, and 25% powdered hog gastric mucin was carried out over the 13-48 degrees temperature range using rotational and creep viscometry. The preparations were almost viscous, and no elastic behavior was demonstrated. The addition of borate ions frequently produced a slight decrease in viscosity. Tetracycline hydrochloride decreased the viscosity of the 10 and 25% materials, although the addition of this compound to fresh gastric and bronchial mucous gels markedly increased viscosity. The model is, therefore, only suitable in limited circumstances as a basis for the evaluation of the effect of drugs on gastric mucus.
The goldfish has been used as a model membrane to estimate the absorption of quinalbarbitone sodium by measurement of overturn time. The effect of sodium cholate, sodium deoxycholate, sodium chenodeoxycholate and sodium taurodeoxycholate on the quinalbarbitone-induced overturn time has been investigated and differences in capacity to promote absorption have been demonstrated. These differences could not be attributed to variations in solubility or partitioning of the drug within the membrane by the bile salts or to the relative hydrophobicity of each molecule. It is suggested that the bile salts must in someway affect the integrity of the goldfish membrane rendering it more permeable to quinalbarbitone sodium.
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