Mohammad A. Khan

Human cervical mucus. I. Rheologic characteristics.

The viscoelastic properties of human cervical mucus were subjected to detailed characterization by microrheometry. An introduced to the range of parameters that can be measured and the sensitivity of microroheometry to variations in mucus viscoelasticity was presented, along with an interpretation of results obtained by this approach. Fresh cervical mucus samples were shown to be rheologically heterogeneous, reflecting compositional differences in situ. Mucas viscoelasticity was stable for several hours when samples were stored at ambient temperature in the microrheometer sample holder. Mucus viscoelasticity was strongly dependent upon nondialyzable solids (NDS) concentration. In order to eliminate (NDS) as a variable in comparative studies of mucus, procedures were developed for reconstitution of mucus at identical (NDS) or for normalization of viscoelasticity data derived from fresh samples to 2.5% NDS. The validity of this approach was then examined by applying these procedures to mucus collected during the follicular, ovulatory, and luteal phases of the normal menstrual cycle.

Human Cervical Mucus. II. Changes in Viscoelasticity During the Ovulatory Menstrual Cycle

Quantitative viscoelasticity measurements were made on individual human cervical mucus samples by microrheometry. Increases in mean values for mucus spinnbarkeit, ferning, and wet weight were associated with the ovulatory phase of the menstrual cycle, while no significant differences versus time were noted for mean values for sample pH or nondialyzable dry weight. A nadir in mucus nondialyzable solids (NDS) concentration and in visoelasticity was seen at or near midcycle. Substantial, highly reproducible, variations in mucus viscoelasticity were observed when mucus from different donors was compared. When the contribution of (NDS) to viscoelasticity was minimized by data normalization or by sample reconstitution, a significant increase in viscoelasticity was associated with the ovulatory phase of the cycle, suggesting the occurrence of a relative increase in mucin concentration or a compositional change in the mucus.

Effect of mucolytic agents on the rheological properties of tracheal mucos

Canine tracheal mucus was dissolved by a number of mucolytic agents, including disulfide bond reducing agents, hydrogen bond breaking agents, and chaotropic ions, and their effect on rheological properties was assessed. Sodium thiocyanate led to 85-100% dissolution with the maximum retention of elasticity. Thiocyanate exposure did not result in demonstrable alterations in the size or shape of the mucus glycoproteins. Sodium thiocyanate is therefore recommended as a suitable dispersing agent for physiochemical studies of glycoprotein secretions.

Functional aspects of mucus rheology.

Mucosal epithelia from all sources are always coated with mucus. Although specific properties of such secretions vary among organ tracts, there are overall chemical and physical similarities which, presumably, reflect a common function. The four types of mucus secretions that have been studied extensively — salivary, gastric, respiratory and cervical — serve a protective function. To this end, the mucus must be dispersed in a thin layer. In addition, specific roles for mucus include particulate clearance and maintenance of proper water balance in the respiratory system, and acting as a barrier and/or reservoir for sperm in the cervix. In order to carry out these functions, the mucus must have particular physical properties that are maintained within suitable bounds. Discussions of the source of mucus secretions and their control are presented in other papers of this symposium.

Human cervical mucus v. oral contraceptives and mucus rheologic properties.

Mucus viscoelasticity on individual samples obtained from patients using combination oral contraceptives was quantitated by microrheometry. These results, in conjunction with mucus chemical characterization, indicate that combination oral contraceptive use eliminates the cyclic variations in mucus chemical, physicochemical, and rheologic properties associated with the ovulatory menstrual cycle. A correlation was demonstrated between the mucus elastic modulus and mucus nondialyzable dry weight, and the mucins produced during oral contraceptive therapy were shown to be similar to those recovered from ovulatory donors. Differences in mucus properties were noted when donors using estrogenic contraceptives were contrasted with those using androgenic contraceptives. On the basis of established relationships between sperm penetrability and mucus solids content, it was concluded that the use of contraceptives, as examined in this study, provided a secondary degree of fertility control at the cervical level.

Rheologic and transport properties of middle ear effusions from cleft palate patients.

Middle ear effusions represent respiratory secretions which are physiologically important to functional mucociliary transport systems. Knowledge of middle ear mucus and methods of facilitating clearance continue to be important to cleft palate patients. Middle ear mucus was collected from the ears of children with cleft palate before surgical correction. Samples were dialyzed and lyophilized to yield mucus powder. This mucus was reconstituted at various nondialyzable solids (NDS) concentrations in TRIS-CI buffer. A physiochemical study of the middle ear mucus was then undertaken, since a mucociliary transport defect leading to serous otitis media (SOM) is an etiologic possibility. The viscoelastic properties of reconstituted middle ear mucus of cleft palate children were determined using a magnetic microrheometer. The relationship to nondialyzable solids concentrations is also described. The mucociliary transport rate as a function of NDS concentrations was recorded on the toad palate model. Results suggest a maximum transport rate at a specific NDS concentration. The viscoelastic properties also correlate well with the mucociliary transport rate. These may have clinical and therapeutic relevance.

Human Cervical Mucus. IV. Viscoelasticity and Sperm Penetrability During the Ovulatory Menstrual Cycle**Supported by National Institutes of Health Contract NO1-HD-4-2838.

Quantitative viscoelastic and sperm penetration measurements were made on individual human cervial mucus samples collected from several ovulatory menstrual cycles. An inverse relationship was found to exist between these two mucus properties, with peak penetrability seen during the ovulatory phase of the cycle when viscoelasticity was lowest. Limited sperm penetration was also observed with follicular phase mucus. When mucus was collected three times daily, the first sample of the day showed reduced pH values and elevated percentage of nondialyzable solids (NDS) and viscoelastcity. Rates of mucus production were calculated for two cycles; the highest rate was seen during the ovulatory phase, with the follicular and luteal phases showing approximately 50% and 30% of this rate, respectively. Limited disparities were noted between midcycle changes in percentage of mucus NDS and viscoelasticity and in blood levels of total estrogens.

Human Cervical Mucus. III. Isolation and Characterization of Rheologically Active Mucin**Supported by United States Public Health Service Grant NO1-HD-4-2838.

Several common mucolytic agents were screened for their ability to solubilize cervical mucus without incurring irreversible losses in mucus viscoelasticity. Sodium thiocyanate was selected on the basis of its effectiveness and handling convenience, and solubilized mucus was fractionated by gel filtration on Sepharose columns. The excluded mucin fraction was characterized by a high neutral hexose to protein ratio and contained all of the elasticity of thiocyanate-treated whole mucus. The concentration of mucin in individual mucus samples collected throughout the ovulatory menstrual cycle was determined from column elution profiles. An increased relative amount of mucin was associated with samples collected during the ovulatory phase of the cycle, and a strong correlation was obtained when the percentage of mucin in individual samples was plotted against their respective storage moduli. These results indicate that the cyclic fluctuations in mucus viscoelasticity seen previously at constant concentrations of nondialyzable solids can be attributed to variations in mucin concentration. Evidence was also obtained, however, for compositional differences in mucus derived from different patients.