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PubMed1989

Human cervical mucus and its interaction with sperm: a fine-structural view.

Cervical mucus is a glycoprotein gel whose biological functions depend upon its macromolecular architecture. Using freeze-substitution fixation techniques, we have used transmission electron microscopy to examine the fine structural aspects of mucus, before and after unidirectional physical shearing, and during its interaction with sperm. The microstructure of mucus that has not been directionally stretched consists of a homogenous pattern of interconnecting electron-dense elements. The thickness of the primary structural elements varies from 0.04 to 0.5 microns, giving the impression that the elements have fibrillar but also ribbon-like properties. This dimension is smaller than the sizes depicted by prior studies using scanning electron microscopy. Within the mucus interior, the interstitial distance between adjacent primary elements ranges from 0.5 to 0.8 microns, and is filled with a fibrous network of secondary structural elements. This interstitial dimension is also significantly smaller than that suggested by prior electron microscopic work. At the exterior borders of the mucus, the interstitial sizes are reduced. After physical stretching by forceps, the mucus microstructure undergoes a radical deformation. In some specimens, the primary structural elements become longitudinally aligned and are less interconnected, with compaction at the exterior mucus borders. In other specimens, the primary structural elements become laterally compressed along the longitudinal axis; within the regions of compression, the intrapore diameter is reduced to less than 0.1 microns. These compressed regions will often exclude spermatozoa. Individual sperm deform the local mucus microstructure. The mucus directly anterior to the sperm head is stretched, and the mucus adjacent to the bending flagellum is compressed on the forward side and stretched on the opposite side.

Cervix Mucus↗
PubMed2000

Effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus in patients undergoing mechanical ventilation.

OBJECTIVE: To evaluate the effects of a heat and moisture exchanger and a heated humidifier on respiratory mucus and transportability by cilia and cough in patients undergoing invasive mechanical ventilation (up to 72 hrs). DESIGN: Prospective, randomized, clinical study. SETTING: General intensive care unit and university research laboratory. PATIENTS: A total of 32 consecutive patients with acute respiratory failure, who were intubated and mechanically ventilated in the intensive care unit setting, were enrolled in the study. INTERVENTIONS: Patients were randomly assigned to receive as a humidifying system a heat and moisture exchanger (HME) or heated humidified water (HHW) at the onset of mechanical ventilation (time 0). Respiratory mucus samples were collected by suction using a sterile technique at time 0, 24, 48, and 72 hrs of mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: Eleven patients were excluded from this study because of either extubation or death before 72 hrs of mechanical ventilation, leaving 12 patients in the HME group and nine patients in the HHW group. Ventilatory variables including minute volume, mean airway pressure, positive end-expiratory pressure, Fio2, as well as Pao2/Fio2 ratio, fluid balance (last 6 hrs), furosemide, and inotrope administration (last 4 hrs) were recorded. In vitro mucus transportability by cilia was evaluated on the mucus-depleted frog palate model, and the results were expressed as the mucus transport rate. Cough clearance (an estimation of the interaction between the flow of air and the mucus lining the bronchial walls) was measured using a simulated cough machine, the results being expressed in millimeters. Mucus wettability was measured by the contact angle between a mucus sample drop and a flat glass surface. Mucus rheologic properties (mechanical impedance [log G*] and the ratio between viscosity and elasticity [tan delta]) were measured using a magnetic microrheometer at 1 and 100 cGy/sec deformation frequency. The two humidification groups were comparable in terms of the Acute Physiology and Chronic Health Evaluation II score, age, gender, ventilatory variables, fluid balance, use of inotropes, and furosemide. CONCLUSION: Ours results indicate that air humidification with either HME or HHW at 32 degrees C (89.6 degrees F) has similar effects on mucus rheologic properties, contact angle, and transportability by cilia in patients undergoing mechanical ventilation, except for transportability by cough, which diminished after 72 hrs of mechanical ventilation in the HME group (p = .0441).

APACHE↗
PubMed1984

Mucus transport and surface damage after endotracheal intubation and tracheostomy. An experimental study in pigs.

The effects on mucus transport of different grades of tracheal injury produced experimentally by an intubation tube were studied in 26 pigs. Two of them were not intubated and served as controls, while the rest were anaesthetized and either intubated or tracheostomized, or both, and ventilated for approximately 4.5 h. They were then killed and the trachea and larynx were immediately removed and placed in a specially designed chamber at 37 degrees C and 85% relative humidity. Cardio-green dye was deposited caudally in the trachea as a mucus marker. The mucus transport was observed macroscopically and the ultrastructure of the tracheal wall at the region of mucus arrest was studied by light microscopy and scanning and transmission electron microscopy. In non-intubated pigs the mucus was transported to the posterior larynx. The ciliated epithelium was usually intact along the pathway where cardio-green-stained mucus had travelled. In pigs which had been intubated and/or tracheostomized, mucus transport stopped completely at different levels of the trachea. The damage to the ciliated epithelium varied; in some animals there was almost none at all and in others there was a patchy loss of a large proportion of the cilia, or complete lack of cilia. Lesions which also included epithelial cells were often seen. Tracheal injury due either to a cuffed endotracheal tube or to a tracheostomy tube, with destruction of epithelium and cilia, causes a barrier to mucus transport, leading to arrest and accumulation of mucus further down in the airway. We were unable, however, to demonstrate a direct correlation between grade of damage and tendency to mucus arrest.

Animals↗
PubMed1984

Role of cervical mucus in human infertility.

The physiological role of cervical mucus in enhancing spermatozoal penetration at mid-cycle has been established. However, the involvement of cervical mucus in primary infertility is still controversial. Although immunological reactions against spermatozoa in the female have been offered to account for the immobilization of spermatozoa--an observation termed 'hostility' of the mucus--this is not always demonstrable. In addition, there are a number of microbial antigens that are similar to spermatozoal antigens. Antibodies to these antigens are found in the serum of the majority of females and males whose infertility is considered to be immunopathological in origin. There are also naturally-occurring antispermatozoal antibodies in both females and males that in some cases may contribute to immunological infertility. The overall spectrum of 'hostile' mucus reactions becomes more complex when we consider the biochemical structure of cervical mucus and its possible interaction with spermatozoa. This spermatozoa: mucus interaction may involve the transfer of spermatozoal components to 'hostile' mucus that should normally be transferred to the zona pellucida of the ova. In addition, there are also pH changes in some 'hostile' mucus that lead to spermatozoal immobilization. In contrast to the above, the cause of infertility in some cases is the inability of spermatozoa to survive in normal mid-cycle mucus. It is evident therefore that an understanding of the complex nature of 'hostile' cervical mucus will lead to a more objective approach in the treatment of infertility.

Antibodies↗
PubMed1987

Intestinal mucus gel and secretory antibody are barriers to Campylobacter jejuni adherence to INT 407 cells.

An in vitro mucus assay was developed to study the role of mucus gel and secretory immunoglobulin A (sIgA) in preventing attachment of Campylobacter jejuni to INT 407 cells. An overlay of rabbit small intestinal mucus was found to impede the attachment of C. jejuni to a monolayer of INT 407 cells. Mucus from rabbits previously colonized with C. jejuni was found to completely inhibit bacterial adherence to the underlying cells. Anti-Campylobacter sIgA was readily detected in mucus samples from previously exposed rabbits and was responsible for eliminating bacterial adherence to the INT 407 cells. This was shown by loss of inhibition after mucus absorption with Campylobacter cells. sIgA-containing mucus caused aggregation of the C. jejuni cells within the mucus layer of the assay system. Nonimmune mucus and sIgA alone were unable to cause bacterial aggregation, suggesting a cooperative role for mucus and sIgA. Antibodies responsible for adhesion inhibition were cross-reactive among several Campylobacter strains and were not directed solely against flagellar antigens.

Animals↗
PubMed1988

Inhibition of attachment of Escherichia coli RDEC-1 to intestinal microvillus membranes by rabbit ileal mucus and mucin in vitro.

Intestinal mucus is postulated to play a role in preventing colonization of the gastrointestinal tract by microbial pathogens. To evaluate the ability of both crude mucus and purified mucin, a glycoprotein of goblet cell origin, to inhibit mucosal adherence of enteric pathogens, we examined whether mucus and mucin derived from rabbit ileum interact with the rabbit enteropathogen Escherichia coli RDEC-1. We examined the manner in which mucus and mucin inhibited adherence of bacteria to rabbit ileal microvillus membranes (MVMs) in vitro. The purity of the mucin preparation was demonstrated by polyacrylamide gel electrophoresis before and after reduction and by showing that an antiserum raised to the mucin localized to goblet cells in rabbit intestine. Using radioactive labeling of bacteria, we quantitated attachment of RDEC-1 to MVMs, mucus, and mucin that had been immobilized on polystyrene microtiter wells. Binding of RDEC-1 to MVMs was also determined after preincubation of organisms with crude ileal mucus and purified mucin. RDEC-1 bound to both crude mucus and purified mucin when they expressed lectinlike adhesions, previously designated attachment factor rabbit 1 pili. Adherence of piliated RDEC-1 to MVMs, mucus, and mucin was significantly greater than when the bacteria were nonpiliated. Binding of piliated RDEC-1 to MVMs was decreased by preincubation of bacteria with both crude mucus (45.6 +/- 4.2% of control) and purified mucin (50.2 +/- 5.8%). These data indicate that the E. coli enteropathogen RDEC-1 can bind to purified glycoproteins of goblet cell origin and that adherence of these bacteria to mucin is mediated by expression of pili. The findings also support a role for intestinal mucus and its principal organic constituent, mucin, in preventing adherence of a known E. coli enteric pathogen to apical MVMs of enterocytes.

Animals↗
PubMed1990

Presence of K88-specific receptors in porcine ileal mucus is age dependent.

Ileal mucus and epithelial cells were isolated from newborn piglets that had never been fed and 35-day-old unweaned piglets. Both newborn and 35-day-old piglet mucus preparations supported growth of Escherichia coli Bd 1107/75 08, a K88-fimbriated porcine enterotoxigenic strain, equally well (i.e., generation times of 28 min were observed in both cases). Adhesion of E. coli Bd 1107/75 08 to 35-day-old piglet ileal epithelial cells was, at most, 2 times that of the same strain to newborn piglet ileal epithelial cells; however, adhesion of E. coli Bd 1107/75 08 to 35-day-old piglet ileal mucus was 16 times that of the same strain to newborn piglet ileal mucus. The receptor in 35-day-old piglet ileal mucus was K88 specific, since it could be removed by purified K88ab fimbriae. Furthermore, adhesion of E. coli Bd 1107/75 08 to 35-day-old piglet ileal mucus was blocked by PAB10, a K88ab-, K88ac-, K88ad-specific monoclonal antibody. Although E. coli Bd 1107/75 08 traversed both newborn and 35-day-old piglet ileal mucus about equally well in vitro and bound well to underlying ileal epithelial cells after passing through newborn ileal mucus, it did not bind to ileal epithelial cells after passing through 35-day-old piglet ileal mucus. The data are discussed with respect to the role that K88-specific receptors present in newborn and ileal mucus might play in the pathogenesis of porcine enterotoxigenic E. coli strains which bear K88 fimbriae.

Aging↗
PubMed2001

The adherent gastrointestinal mucus gel layer: thickness and physical state in vivo.

Divergent results from in vitro studies on the thickness and appearance of the gastrointestinal mucus layer have previously been reported. With an in vivo model, we studied mucus gel thickness over time from stomach to colon. The gastrointestinal tissues of Inactin-anesthetized rats were mounted luminal side up for intravital microscopy. Mucus thickness was measured with a micropipette before and after mucus removal by suction. The mucus layer was translucent and continuous; it was thickest in the colon (approximately 830 microm) and thinnest in the jejunum (approximately 123 microm). On mucus removal, a continuous, firmly adherent mucus layer remained attached to the epithelial surface in the corpus (approximately 80 microm), antrum (approximately 154 microm), and colon (approximately 116 microm). In the small intestine, this layer was very thin (approximately 20 microm) or absent. After mucus removal, there was a continuous increase in mucus thickness with the highest rate in the colon and the lowest rate in the stomach. In conclusion, the adherent gastrointestinal mucus gel in vivo is continuous and can be divided into two layers: a loosely adherent layer removable by suction and a layer firmly attached to the mucosa.

Animals↗
PubMed1985

Clearance of mucus by simulated cough.

We examined the relationship between mucus rheology, depth of mucus layer, and clearance by simulated cough. A model trachea was constructed of rigid Plexiglas of rectangular cross section (1 X 2 X 35 cm). The bottom of the trachea was lined with mucus simulants, gels prepared from locust bean gum cross-linked with sodium borate. Cough was simulated by opening a solenoid valve connecting the model trachea to a pressurized tank. An upstream flow-constrictive element was used to shape the flow profile of the simulated cough to approximate the pattern seen in a normal adult. Clearance of mucus was quantitated by observing the movement of contrasting marker particles floating in the mucus layer. The median particle displacement per cough maneuver was defined as the clearance index (CI). We found that CI for any initial depth of mucus increased with the driving pressure in the tank. For a given driving pressure, CI increased linearly with increasing mucus depth. For a given driving pressure and depth, CI decreased with increasing mucus cross-link density. For mucus samples with comparable levels of dynamic viscosity, samples with higher elasticity cleared less well. Mucus clearance was associated with transient wave formation in the lining layer.

Cough↗
PubMed1986

Mucus transport in the airways by two-phase gas-liquid flow mechanism: continuous flow model.

Mucus transport speed induced by two-phase gas-liquid interaction was measured in the continuous two-phase annular flow tube models, and factors influencing the transport speed were assessed in conjunction with rheological properties of mucus. The flow model was made with 1.0-cm-ID glass tubes and positioned either vertically or horizontally. During a continuous passage of airflow through the model tube, mucus stimulants were supplied into the tube at a rate of 0.5-2.0 ml/min. The advancing speed of the leading edge of the mucous layer and mean mucous layer thickness were then measured. The transport speed in the vertical tube model ranged from 1.1 to 3.1 cm/min with a mucus feed rate of 0.5 ml/min at airflow rates of 0.33-1.17 l/s and increased with increasing airflow rates but decreased rapidly with increasing viscosity of mucus. The transport speed increased almost proportionally with increasing mucus feed rate. Elasticity of mucus did not affect the transport speed itself. However, more elastic mucus caused lower flow resistance and thereby could be transported with a much reduced work load. The transport speed in the horizontal tube model was 5-60% faster than that in the vertical tube model. The mean mucous layer thickness in the vertical tube model was found to be in the range of 0.5-1.5 mm in the experimental conditions used, and decreased rapidly with increasing airflow rate and decreasing viscosity of mucus. From these data the transport speed could be functionally related to airway diameter, mucous layer thickness, and mucus production rate.

Biological Transport↗
PubMed1988

Mucus transport by high-frequency nonsymmetrical oscillatory airflow.

To study air-mucus interaction as a possible mechanism of tracheal mucus transport and to test the validity of using surface tracer displacement to indicate bulk mucus transport, we performed a combined experimental-theoretical study. We hypothesized that the mucus mass is moved by the difference between expiratory and inspiratory velocities. The rate of transport of a layer of simulated mucus lining the bottom of a rectangular trough was measured in two ways during oscillatory air flow. Peak velocity ratios (R) from 1.0 to 2.0, frequencies (f) between 7 and 13 Hz, and tidal volumes (VT) between 50 and 100 ml were generated by a custom-made pump. The experimental results demonstrate that measuring the displacement of a tracer deposited on the surface of the mucus layer is equivalent to measuring bulk mucus movement by weight. Moreover the measured mucus velocities (micron) correlate well with a theoretical model which predicts that micron is proportional to delta VT f1.5 (R-1). These results suggest that shearing at the air-mucus interface could be a significant factor in the enhanced tracheal mucus clearance during high-frequency chest wall oscillation.

Animals↗
PubMed1998

Coordinated clearance of periciliary liquid and mucus from airway surfaces.

Airway surface liquid is comprised of mucus and an underlying, watery periciliary liquid (PCL). In contrast to the well-described axial transport of mucus along airway surfaces via ciliary action, theoretical analyses predict that the PCL is nearly stationary. Conventional and confocal microscopy of fluorescent microspheres and photoactivated fluorescent dyes were used with well-differentiated human tracheobronchial epithelial cell cultures exhibiting spontaneous, radial mucociliary transport to study the movements of mucus and PCL. These studies showed that the entire PCL is transported at approximately the same rate as mucus, 39.2+/-4.7 and 39.8+/-4.2 micrometer/sec, respectively. Removing the mucus layer reduced PCL transport by > 80%, to 4.8+/-0.6 micrometer/sec, a value close to that predicted from theoretical analyses of the ciliary beat cycle. Hence, the rapid movement of PCL is dependent upon the transport of mucus. Mucus-dependent PCL transport was spatially uniform and exceeded the rate expected for pure frictional coupling with the overlying mucus layer; hence, ciliary mixing most likely accelerates the diffusion of momentum from mucus into the PCL. The cephalad movement of PCL along airway epithelial surfaces makes this mucus-driven transport an important component of salt and water physiology in the lung in health and disease.

Biological Transport↗
PubMed1995

Chronic mucus hypersecretion in COPD and death from pulmonary infection.

The association of chronic mucus hypersecretion and mortality is a matter of debate. We wished to determine whether the relationship between chronic mucus hypersecretion and chronic obstructive pulmonary disease (COPD)-related mortality could be explained by proneness to pulmonary infection. We followed 14,223 subjects of both sexes for 10-12 yrs. Cases where COPD was an underlying or contributory cause of death (n = 214) were included, and hospital records were obtained when possible (n = 101). From the presence of increased mucus, purulent mucus, fever, leucocytosis and infiltration on chest radiography, death was classified as either due to pulmonary infection (n = 38), other causes (n = 51), or unclassifiable (n = 12). Of subjects reporting chronic mucus hypersecretion at the initial examination, pulmonary infection was implicated in 54% of deaths, whereas this only occurred in 28% of subjects without chronic mucus hypersecretion. Controlling for covariates, in particular smoking habits, a Cox analysis showed a strong inverse relationship between ventilatory function and COPD-related mortality. Chronic mucus hypersecretion was found to be a significant predictor of COPD-related death with pulmonary infection implicated (relative risk (RR) 3.5) but not of death without pulmonary infection (RR 0.9). We consider that subjects with COPD and chronic mucus hypersecretion are more likely to die from pulmonary infections than subjects without chronic mucus hypersecretion. This may explain the excess mortality in subjects with COPD and chronic mucus hypersecretion found in previous studies.

Cause of Death↗
PubMed1991

Separation of mounting-inducing pheromones of vaginal mucus from estrual heifers.

There is evidence that mucus of the female bovine genital tract contains pheromones that induce physiological and behavioral responses in other animals. To study these pheromones, vaginal mucus was collected from heifers either at estrus or during diestrus. The mucus was then applied to the hindquarters of the same animal during diestrus or to the hindquarters of herdmates during diestrus. The behaviors of the treated animal and its herdmates were then observed. To attempt to isolate the mounting-inducing substance, mucus was dialyzed or separated on ion-exchange resins. Diestrous heifers to which their own estrual mucus has been applied were nearly always mounted by herdmates (P less than .01). But, heifers to which another's estrous mucus had been applied were not mounted. This suggests that vaginal mucus contains not only estrus-related pheromones, but also individual distinctive odors. The dialyzable fraction of vaginal mucus and the neutral fraction, prepared by ion-exchange chromatography of the dialyzable solution of vaginal mucus, had a mounting-inducing activity on the herdmates, as did the application of an animal's own vaginal mucus. These findings suggest that mounting-inducing pheromones are relatively low molecular weight, neutral substances.

Animals↗
PubMed2000

Tracheobronchial mucus viscoelasticity during environmental challenge in horses with recurrent airway obstruction.

The goal of this study was to compare the rheological properties of mucus from horses with recurrent airway obstruction (RAO) to that from healthy controls during environmental challenge by stabling in stalls with straw as bedding and hay as feed. We determined viscoelasticity (log G* dyn/cm2, at 10 radian/s) and calculated mucociliary clearability index (MCI) and cough clearability index (CCI), which are derivative parameters of G* and the ratio of viscosity and elasticity measured at 1 and 100 radian/s, respectively. We also investigated the solids content of mucus, and cytology of bronchoalveolar lavage fluid (BALF). Samples were obtained before (0 h) and 6, 24 and 48 h after environmental challenge. The central findings were rheological changes in airway mucus, which occurred over time in RAO-affected animals, but not in controls. Mucus rheology was similar in both groups at 0 and 6 h. In RAO-affected horses, mucus viscoelasticity, as measured by log G*, increased from 2.49 +/- 0.18 dyn/cm2 (mean +/- s.e.) at 0 h to 3.05 +/- 0.13 dyn/cm2 at 24 h after environmental challenge, and was accompanied by significant decreases in MCI and CCI. Percent solids of mucus did not differ significantly between the 2 groups, nor over time. Rheological values did not correlate with BALF cytology. We conclude that viscoelastic properties of tracheal mucus samples from RAO horses in remission do not differ from those of normal horses. However, environmental challenge causes clinical signs of small airway disease and a concurrent increase in mucus viscoelasticity only in RAO horses. Therefore, we infer that unfavourable changes in mucus rheology may contribute to stasis and accumulation of mucus in RAO horses in exacerbation, but not in clinical remission.

Airway Obstruction↗
PubMed1989

The measurement of gastric mucus using a computer image processing system.

The measurement of gastric mucus, and the effects of aspirin and some antiulcer drugs on the content or components of gastric mucus were investigated in normal rats by using a newly devised computer image processing system. The present method enabled us to separate mucus components into PAS positive mucus (PAS+), and AB positive mucus (AB+), and to measure the amount of each mucus. Aspirin induced significant decreases in both PAS+ and AB+, teprenone increased the total amount of gastric mucus (PAS+ plus AB+), secretin tended to increase AB+, and cimetidine and omeprazole caused no remarkable changes on mucus secretion. These changes in gastric mucus could be observed on both microscopic observation and with the computer image processing system. The results indicate that the computer image processing system is very useful for the measurement of gastric mucus.

Animals↗
PubMed1990

Tracheal mucus rheology and epithelial potential difference in two day old puppies.

The transepithelial potential difference (PD) value represents an integral of ion fluxes across the epithelium, and relates to the regulation of airway fluid. We studied six healthy two day old husky puppies for their tracheal mucus rheology and bioelectric properties, since this data in newborns are still unknown. PD (-mV, epithelium vs. subcutaneous space) was measured using the agar bridge technique in two locations - lower trachea and subglottic region. For the rheological analysis, the magnetic microrheometer was employed; data are presented as mechanical impedance log G* and loss tangent tan delta (1 rad/s). The mucus collection rate (mg/min) and the solid content (%) were determined by gravimetry. Mucociliary clearability, normalized to frog mucus, (MCFP) was determined directly by the frog palate method; a cough clearability index (CCI) was computed from simulated cough machine data obtained with mucus-like gels. The mucus collection rates and PD values were considerably lower than those observed in adult dogs; the mechanical impedance values were also reduced in comparison with adult data. The PD profile within the trachea (-13.9 +/- 1.2 mV lower trachea vs. -18.4 +/- 1.4 mV subglottical, i.e. more negative subglottically), however, is similar to that observed in adult dogs. Intratracheal profiles in mucus collection rate and mucus rheology were also comparable between puppies and adult dogs. The low collection rates in puppies, particularly in lower trachea, could indicate either reduced mucus volume or slower clearance. PD and collection rate correlated very strongly (r = 0.82, p = 0.0003). PD also correlated negatively with log G* (r = 0.73, p = 0.003) and positively with tan delta (r = 0.58, p = 0.03). MCFP and % solids correlated positively (r = 0.84, p = 0.0012), in contradistinction to the usual relationship, perhaps due to the presence of non-glycoprotein components that do not contribute to crosslink formation. The apparent maturation of airway bioelectric properties, mucus collection rate and mucus viscoelasticity are all consistent with the maturation of mucociliary clearance, which has previously been reported.

Animals↗
PubMed2000

Changes in hydrolytic enzyme activities of naïve Atlantic salmon Salmo salar skin mucus due to infection with the salmon louse Lepeophtheirus salmonis and cortisol implantation.

The changes in the activities of mucus hydrolytic enzymes and plasma cortisol levels were examined following infection of Atlantic salmon Salmo salar with the salmon louse Lepeophtheirus salmonis and these changes were compared with those resulting from elevated plasma cortisol. Salmon were infected at high (Trial 1; 178 +/- 67) and low (Trial 2; 20 +/- 13) numbers of lice per fish and the activities of proteases, alkaline phosphatase, esterase and lysozyme in the mucus, as well as plasma cortisol levels were determined. At both levels of infection, there were significant increases of protease activity over time (1-way K-WANOVA; Trial 1, p = 0.004; Trial 2, p < 0.001). On several sampling days, generally on later days in the infections, the mucus protease activities of infected fish were significantly higher than control fish (Student's t-tests; p < 0.05). In addition, zymography experiments demonstrated bands of proteases at 17 to 22 kDa in the mucus of infected salmon that were absent in the mucus from non-infected fish and absent in the plasma of salmon. The intensity of these protease bands increased in the mucus over the course of both infections. However, plasma cortisol levels were elevated only in the heavily infected fish from the first trial. At high infection levels (Trial 1), alkaline phosphatase activity was higher in the mucus of infected fish at all days (t-test, p < 0.05). However, at the lower infection level (Trial 2), the mucus alkaline phosphatase activity did not differ significantly between infected and non-infected fish. Esterase and lysozyme activities were very low and did not change with time nor between non-infected and infected salmon in either challenge. Mucus enzyme activities of cortisol-implanted salmon did not change over time, nor were there any differences in activities between cortisol-implanted and control salmon. The present study demonstrates biochemical changes resulting from sea lice infection of Atlantic salmon occurring at the site of host-pathogen interaction, the mucus layer. However, the origin of these enzymes, whether host or pathogen, remains to be determined.

Alkaline Phosphatase↗