Everything you wanted to know about the bladder epithelium but were afraid to ask

The mammalian urinary bladder epithelium (urothelium) performs the important function of storing urine for extended periods, while maintaining the urine composition similar to that delivered by the kidneys. The urothelium possesses four properties to perform this function. First, it offers a minimum epithelial surface area-to-urine volume; this reduces the surface area for passive movement of substances between lumen and blood. Second, the passive permeability of the apical membrane and tight junctions is very low to electrolytes and nonelectrolytes. Third, the urothelium has a hormonally regulated sodium absorptive system; thus passive movement of sodium from blood to urine is countered by active sodium reabsorption. Last, the permeability properties of the apical membrane and tight junctions of the urothelium are not altered by most substances found in the urine or blood. The importance of the barrier function of the urothelium is illustrated by infectious cystitis. The loss of the barrier function results in the movement of urinary constituents into the lamina propria and underlying muscle layers, resulting in suprapubic and lower back pain and frequent, urgent, and painful voiding.

First Reports of Aphelenchoides fragariae on Royal Fern and on Hosta and Other Hosts in South Carolina

In September 1999, royal ferns (Osmunda regalis L.) at a South Carolina wholesale nursery were found to be infected by foliar nematodes. Lesions were brown, vein-limited, and often fan shaped. As severity increased, affected leaflets became totally necrotic. Nematodes were extracted by excising and dicing symptomatic leaf sections and placing them in water for up to 24 h. Ten adult nematodes from each of two fern plants were examined microscopically and determined to be Aphelenchoides fragariae (Ritzema Bos) Christie. This is the first report of this nematode infecting royal fern. In August 1996, leaves from several cultivars of Hosta spp. with yellow to tan, vein-limited lesions were submitted from The South Carolina Botanical Garden (Clemson, SC) to the Clemson University Plant Problem Clinic for diagnosis. Nematodes were extracted and examined as described above and identified as A. fragariae. This is the first report of this nematode infecting Hosta spp. in South Carolina. Since 1996, foliar nematodes have been recovered from hostas at several wholesale nurseries in South Carolina. Aphelenchoides spp. also have been detected previously in commercially produced ornamental plants in South Carolina, including a Begonia sp. in 1988; Polygonum bistorta L. 'Super-bum' (snakeweed) in 1997; and a Polystichum sp. (holly fern) in 1997. All plants exhibited angular or vein-limited, necrotic lesions typical of foliar nematode infections.

Inhaled corticosteroid use and bone-mineral density in patients with asthma

BACKGROUND

Inhaled corticosteroids are absorbed into the systemic circulation, but the extent to which they have adverse effects on bone is uncertain. The question is important since 3% of the European population take an inhaled corticosteroid regularly and may do so for many years.

METHODS

We studied the dose-response relation between cumulative inhaled corticosteroid dose and bone-mineral density at the lumbar spine and proximal femur in 196 adults (119 women) with asthma aged 20-40 years. Patients had taken an inhaled corticosteroid regularly for at least 6 months, and had had limited exposure to systemic steroids. Cumulative dose of inhaled corticosteroid was calculated from questionnaires and computerised and written general-practice records, and its effect on bone-mineral density was estimated by multiple regression analysis.

FINDINGS

Median duration of inhaled corticosteroid treatment was 6 years (range 0.5-24), and median cumulative dose was 876 mg (87-4380). There was a negative association between cumulative dose of inhaled corticosteroid and bone-mineral density at the lumbar spine (L2-L4), femoral neck, Ward's triangle, and trochanter, both before and after adjustment for the effects of age and sex. A doubling in dose of inhaled corticosteroid was associated with a decrease in bone-mineral density at the lumbar spine of 0.16 SD (95% CI 0.04-0.28). Similar decreases were found at the femoral neck, Ward's triangle, and trochanter. Adjustment for potential confounding factors including physical activity and past oral, nasal, dermal, and parenteral corticosteroids did not weaken the associations.

INTERPRETATION

This study provides evidence of a negative relation between total cumulative dose of inhaled corticosteroid and bone-mineral density in patients with asthma.

Temperature-dependent gain and noise in fiber Raman amplifiers

An experimental investigation of the temperature dependence of the gain and noise performance of a silica-fiber Raman amplifier is described. A decrease in the Raman scattering cross section in a fiber amplifier cooled from a temperature of 300 K to 77 K was measured and found to be in agreement with theoretical values. No difference between the Raman gain coefficients at these two temperatures was observed.

A chaperone with a hydrophilic surface

The folding of native tubulin involves at least seven different chaperone proteins: prefoldin, the cytosolic chaperonin CCT and five tubulin-specific chaperone proteins named cofactors A-E. The structure of the yeast homolog of cofactor A, Rbl2p, shows it to be a dimer with largely hydrophilic surfaces, reflecting the fact that it interacts with quasi-native, not unfolded, beta-tubulin.

Potassium nitrite reaction with 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid in urine in relation to the drug screening analysis

Recently potassium nitrite has been used as an adulterant to interfere with the analysis of 11-nor-delta 9-tetrahydro-cannabinol-9-carboxylic acid (THC-COOH) in urine. A comprehensive study of the THC-COOH and nitrite reaction chemistry and stability under various conditions is presented. Reverse phase high performance liquid chromatography (HPLC) and negative electrospray mass spectrometry (ESMS) results are given to substantiate the derived reaction mechanism and properties leading to reaction termination. The addition of potassium carbonate as a buffering agent prior to or following sample void as a means of preventing the formation of a nitroso-complexed form of the 11-nor-delta 9+-tetrahydrocannabinol-9-carboxylic acid is evaluated.

Tubulin folding cofactors as GTPase-activating proteins. GTP hydrolysis and the assembly of the alpha/beta-tubulin heterodimer

In vivo, many proteins must interact with molecular chaperones to attain their native conformation. In the case of tubulin, newly synthesized alpha- and beta-subunits are partially folded by cytosolic chaperonin, a double-toroidal ATPase with homologs in all kingdoms of life and in most cellular compartments. alpha- and beta-tubulin folding intermediates are then brought together by tubulin-specific chaperone proteins (named cofactors A-E) in a cofactor-containing supercomplex with GTPase activity. Here we show that tubulin subunit exchange can only occur by passage through this supercomplex, thus defining it as a dimer-making machine. We also show that hydrolysis of GTP by beta-tubulin in the supercomplex acts as a switch for the release of native tubulin heterodimer. In this folding reaction and in the related reaction of tubulin-folding cofactors with native tubulin, the cofactors behave as GTPase-activating proteins, stimulating the GTP-binding protein beta-tubulin to hydrolyze its GTP.

Eosinophil peroxidase increases membrane permeability in mammalian urinary bladder epithelium

Eosinophil peroxidase (EPO), a cationic protein found in eosinophils, has been reported to be cytotoxic independent of its peroxidase activity. This study investigated with electrophysiological methods whether EPO is toxic to mammalian urinary bladder epithelium. Results indicate that EPO, when added to the mucosal solution, increases apical membrane conductance of urinary bladder epithelium only when the apical membrane potential is cell interior negative. The EPO-induced conductance was concentration dependent, with a maximum conductance of 411 microseconds/cm2 and a Michaelis-Menten constant of 113 nM. The EPO-induced conductance was nonselective for K+ and Cl-. The conductance was partially reversed using voltage but not by removal of EPO from the bulk solution. Mucosal Ca2+ reversed the EPO-induced conductance by a mechanism involving reversible block of the conductance. Prolonged exposure (up to 1 h) to EPO was toxic to the urinary bladder epithelium, as indicated by an irreversible increase in transepithelial conductance. These results suggest that EPO is indeed toxic to urinary bladder epithelium via a mechanism that involves an increase in membrane permeability.

Tactile illusion-produced number perception in blind and sighted persons

OBJECTIVE

To determine whether tactile receptive communication is possible in both sighted and blind persons through the use of a mechanical device that creates the perception of continuous contact through sequential points of vibration on the skin and whether the ability of these two groups differs.

MATERIAL AND METHODS

The cohort consisted of 20 sighted and 20 blind subjects who had no prior exposure to a tactile communication device that produces a tactile illusion. Each subject was presented number sequences created by the tactile illusion in the form of single-digit, three-digit, and four-digit sequences, and the number of trials needed for correct identification was recorded.

RESULTS

On average, the sighted subjects tended to identify the digit sequences sooner than did the blind subjects by almost one trial; however, this difference was not statistically significant. Younger subjects and female subjects also tended to identify the digit sequences sooner. Nevertheless, the overall correlation between age and number of trials across all replications was relatively minor.

CONCLUSION

Tactile receptive communication is possible through the use of a mechanical device used to create tactile illusions. The tactile illusion of numbers is equally perceived by blind and sighted persons.

Measles infection, measles vaccination and the effect of birth order in the aetiology of hay fever

BACKGROUND

It has recently been suggested that measles infection may reduce the risk of atopy.

OBJECTIVE

To study the independent effect of measles infection and measles vaccination on the occurrence of hay fever in a British national birth cohort.

METHODS

In over 6000 children born in 1970, details of immunizations and childhood diseases were collected by parental interviews at ages 5, 10 and 16 years, and hay fever within the past year at age 16 years.

RESULTS

In univariate analysis, hay fever was less common in those contracting measles infection than in those not infected (OR 0.86, 95% CI 0.76-0.96), and more common in those given measles vaccination than in those not vaccinated (OR 1.16, 95% Cl 1.03-1.31). However, these effects were strongly confounded by birth order, which was closely associated with the likelihood of receiving measles vaccination and with the risk of hay fever. A strong interaction between the effects of measles vaccination and infection, and birth order was found, such that in those with many older sibling contacts, hay fever was significantly and independently reduced in relation to both measles infection and measles vaccination relative to those who were neither infected nor vaccinated.

CONCLUSIONS

Both measles infection and measles vaccination in childhood appear to reduce the risk of hay fever in children with multiple older sibling contacts. Differential exposure or response to the measles virus may explain the effect of birth order on the occurrence of allergic disease.

Diversity Among a Heterodera glycines Field Isolate and Derived Inbreds Based on RAPD Analysis and Reproduction on Soybean Genotypes

A field population of Heterodera glycines was inbred by a combination of controlled male-female matings and inoculation of soybean with second-stage juveniles (J2) from single cysts. The initial and four F inbred populations were subjected to random amplified polymorphic DNA analysis and were also tested for their ability to reproduce on race differentials. The RAPD patterns of the inbred populations had a lower number of total bands and a lower percentage of polymorphic bands among individual cysts than the initial population. The estimated number of polymorphic loci detected by RAPD analysis was about 25% for the initial population and 4% to 7% for the inbred lines. Reproduction of H. glycines decreased for 6 of 24 inbred-soybean combinations. In particular, reproduction of three inbred populations on PI 90763 was greatly reduced. Inbreeding did not decrease variance of cyst number on soybean genotypes. The inbreeding coefficient calculated from RAPD data was greater than that derived from the known inbreeding pedigree.

Consistent effects of high socioeconomic status and low birth order, and the modifying effect of maternal smoking on the risk of allergic disease during childhood

Birth order, maternal age, gestational age, birth weight, maternal smoking, and social class have all been associated with allergic rhinitis, eczema and asthma in childhood, but the consistency of independent effects of these exposures in relation to all of these allergic conditions has not been investigated. We have compared and contrasted the independent effects of these putative risk factors on parent-reported hayfever, eczema and wheeze by age 16 years and in the past 12 months at age 16 using data from the 1970 British birth cohort. The 1970 British birth cohort comprised all children born in England, Scotland and Wales in one week of April 1970, and follow-up surveys at birth, 5, 10 and 16 years of age involved a cumulative total of 17,427 children. We have used data on over 6000 children with complete data at every stage. Social advantage was a risk factor common to each of wheeze at, and hayfever and eczema at and by age 16. Low birth order was an independent risk factor for eczema and hayfever at age 16, but not for wheeze. However, wheeze at age 16 was significantly increased in relation to maternal smoking, with a significant interaction such that the effect of smoking was greatest in those of high birth order and, in the absence of maternal smoking, low birth order was a risk factor for wheeze at age 16. Social advantage and low birth order appear to be the independently consistent determinants of atopic disease. Maternal smoking is an additional risk factor for wheeze, which applies primarily in low socioeconomic groups.

Modulation of polymyxin B effects on mammalian urinary bladder

This report demonstrates that Ca2+, Mg2+, and protons alter the ability of polymyxin B (PX, a cationic antibiotic used clinically as a bactericidal agent) to increase the apical membrane conductance of the rabbit urinary bladder. Using electrophysiological methods, we determine that these alterations occur by two mechanisms. First, they blocked the PX-induced conductance in a rapid and reversible manner; second, they competed with PX for a membrane binding site. In addition, Ca2+ (but not Mg2+ or protons) altered the rate at which the induced conductance could be reversed. When solution pH was greater than 8.8, PX was not able to induce a conductance. This ability of high pH to inhibit the action of PX was due to a decrease in the number of positive charges on PX. Further studies demonstrated that for maximal activity, PX required its fatty acid tail. These data were used to develop a model describing the mechanism by which PX can induce a conductance in the apical membrane of the rabbit urinary bladder.

Eosinophil major basic protein increases membrane permeability in mammalian urinary bladder epithelium

The eosinophil granule protein major basic protein (MBP) is toxic to a wide variety of cell types, by a poorly understood mechanism. To determine whether the action of MBP involves an alteration in membrane permeability, we tested purified MBP on rabbit urinary bladder epithelium using transepithelial voltage-clamp techniques. Addition of nanomolar concentrations of MBP to the mucosal solution caused an increase in apical membrane conductance only when the voltage across the apical membrane was cell interior negative. The magnitude of the MBP-induced conductance was a function of MBP concentration, and the rate of the initial increase in conductance was a function of the transepithelial voltage. The MBP-induced conductance was nonselective for K+ and Cl-. Mucosal Ca2+ reversed the induced conductance, whereas mucosal Mg2+ partially blocked the induced conductance and slowed the rate of the increase in conductance. The induced conductance was partially reversed by changing the voltage gradient across the apical membrane to cell interior positive. Prolonged exposure resulted in an irreversible loss of the barrier function of the urinary bladder epithelium. These results suggest that an increase in cell membrane ion permeability is an initial step in MBP-induced loss of barrier function.

Inoculation Method for Studying Early Responses of Glycine max to Heterodera glycines

An inoculation technique was developed for studying molecular responses of soybean to the soybean cyst nematode (Heterodera glycines). Effect of inoculum age (0-7 days after eggs were released from cysts) and inoculation site (meristem, elongation, or differentiation zone) on infection were tested on four soybean genotypes. Two genotypes (PI 437654 and cv. Peking) were resistant and two (cv. Essex and cv. Hutcheson) were susceptible to race 3 of H. glycines. Inoculum consisting of second-stage juveniles (J2) was prepared by gently agitating nematode eggs at 75 revolutions per minute at 28 degrees C for various intervals. Infection rates were monitored cytologically. The most consistent infection rate was obtained with 48-hour-old inoculum containing more than 80% J2. More than 100 juveniles/root were observed after inoculation with the 48-hour-old inoculum placed at the root elongation zone, in both resistant and susceptible soybeans. Horizontal orientation of roots during inoculation, the use of concentrated J2 inoculurn (500 J2 in 125 mul/root), and restriction of inoculum to the root elongation zone facilitated synchronous root infection.

Prefoldin, a chaperone that delivers unfolded proteins to cytosolic chaperonin

We describe the discovery of a heterohexameric chaperone protein, prefoldin, based on its ability to capture unfolded actin. Prefoldin binds specifically to cytosolic chaperonin (c-cpn) and transfers target proteins to it. Deletion of the gene encoding a prefoldin subunit in S. cerevisiae results in a phenotype similar to those found when c-cpn is mutated, namely impaired functions of the actin and tubulin-based cytoskeleton. Consistent with prefoldin having a general role in chaperonin-mediated folding, we identify homologs in archaea, which have a class II chaperonin but contain neither actin nor tubulin. We show that by directing target proteins to chaperonin, prefoldin promotes folding in an environment in which there are many competing pathways for nonnative proteins.

Tumor necrosis factor-alpha increases sodium and chloride conductance across the tight junction of CACO-2 BBE, a human intestinal epithelial cell line

CACO-2 BBE was used to determine the response of a gastrointestinal epithelium to tumor necrosis factor-alpha (TNF). Incubation of CACO-2 BBE with TNF did not produce any effect on transepithelial resistance (TER) within the first 6 hr but resulted in a 40-50% reduction in TER and a 30% decrease in 1SC (short circuit current) relative to time-matched control at 24 hr. The decrease in TER was sustained up to 1 week following treatment with TNF and was not associated with a significant increase in the transepithelial flux of [14C]-D-mannitol or the penetration of ruthenium red into the lateral intercellular space. Dilution potential and transepithelial 22Na+ flux studies demonstrated that TNF-treatment of CACO-2 BBE cell sheets increased the paracellular permeability of the epithelium to Na+ and Cl-. The increased transepithelial permeability did not associate with an increase in the incidence of apoptosis. However, there was a TNF-dependent increase in [3H]-thymidine labeling that was not accompanied by a change in DNA content of the cell sheet. The increase in transepithelial permeability was concluded to be across the tight junction because: (i) 1 mM apical amiloride reduced the basolateral to apical flux of 22Na+, and (ii) dilution potential studies revealed a bidirectionally increased permeability to both Na+ and Cl-. These data suggest that the increase in transepithelial permeability across TNF-treated CACO-2 BBE cell sheets arises from an alteration in the charge selectivity of the paracellular conductive pathway that is not accompanied by a change in its size selectivity.

Histone-induced damage of a mammalian epithelium: the role of protein and membrane structure

In a previous report [T. J. Kleine, A. Gladfelter, P. N. Lewis, and S. A. Lewis, Am. J. Physiol. 268 (Cell Physiol. 37): C1114-C1125, 1995], we found that the cationic DNA-binding proteins histones H4, H1, and H5 caused a voltage-dependent increase in the transepithelial conductance in rabbit urinary bladder epithelium. In this study, results from lipid bilayer experiments suggest that histones H5-H1 and H4 form variably sized conductive units. Purified fragments of histones H4 and H5 were used to determine the role of histone tertiary structure in inducing conductance. Isolated COOH- and NH2-terminal tails of histone H4, which are random coils, were inactive, whereas the central alpha-helical domain induced a conductance increase. Although the activities of the central fragment and intact histone H4 were in many ways similar, the dose-response relationships suggest that the isolated central domain was much less potent than intact histone H4. This suggests than the NH2- and COOH-terminal tails are also important for histone H4 activity. For histone H5, the isolated globular central domain was inactive. Thus the random-coil NH2- and COOH-terminal tails are important for H5 activity as well. These results indicate that histone molecules interact directly with membrane phospholipids to form a channel and that protein tertiary structure and the degree of positive charge play an important role in this activity.

Cross sectional investigation of the effects of inhaled corticosteroids on bone density and bone metabolism in patients with asthma

BACKGROUND

Bone mineral density has been reduced in patients with asthma taking inhaled corticosteroids in some cross sectional studies and this could be important if treatment is continued for several decades. The possibility of confounding by age, menopausal status, physical activity and, especially, past oral steroid use has not been excluded in most studies. The present study was designed to assess the magnitude of any reduction in bone mineral density in relation to inhaled steroid use after adjusting for these factors.

METHODS

Bone mineral density (BMD), vertebral fractures, and markers of bone metabolism (serum osteocalcin, procollagen peptide I, bone-specific alkaline phosphatase, and urinary deoxypyridinoline cross links) were measured in 81 patients with asthma age 20-40 years; 34 patients (19 men) who had never had inhaled or systemic steroids and 47 (19 men) who had taken inhaled steroids for at least five years with limited exposure to systemic steroids in the past. Data relating to past medication use, physical activity, smoking, and other confounding factors were collected by questionnaire. The relation between inhaled steroid dose and duration and BMD was assessed by linear regression analysis, accounting for potential confounders including weight, exercise, and oral steroid use.

RESULTS

The 47 patients taking an inhaled steroid had a mean current dose of 620 micrograms/day (range 100-3000 micrograms), a mean duration of use of 7.8 years, and had had a mean of 0.85 courses of prednisolone in the past. There was no significant difference in mean BMD values between those who were and those who were not on inhaled steroids in men or women. However, on multivariate analysis, cumulative inhaled steroid dose was associated with a reduction in posterior-anterior (P-A) and lateral lumbar spine bone mineral density in women, equivalent to a 0.11 standard deviation reduction in bone density per 1000 micrograms/day inhaled steroid per year after adjustment for potential confounding factors (95% CI for P-A spine 0.01 to 0.22; for lateral spine 0.02 to 0.21). Previous oral steroid use was not an important confounding factor in these patients. Inhaled steroid use was not related to BMD at the wrist or hip in women or at any skeletal site in men. Women taking an inhaled steroid had lower levels of serum osteocalcin than those not taking them, although this was not dose related. Inhaled steroid use was not associated with differences in other markers of bone metabolism in men or women or with the presence of vertebral fractures.

CONCLUSIONS

Although an effect of confounding factors cannot be excluded entirely in a cross sectional study, our findings are in keeping with an effect of inhaled steroid therapy in reducing bone density in the spine in women and provide an estimate of the magnitude of this effect.

Tubulin subunits exist in an activated conformational state generated and maintained by protein cofactors

The production of native alpha/beta tubulin heterodimer in vitro depends on the action of cytosolic chaperonin and several protein cofactors. We previously showed that four such cofactors (termed A, C, D, and E) together with native tubulin act on beta-tubulin folding intermediates generated by the chaperonin to produce polymerizable tubulin heterodimers. However, this set of cofactors generates native heterodimers only very inefficiently from alpha-tubulin folding intermediates produced by the same chaperonin. Here we describe the isolation, characterization, and genetic analysis of a novel tubulin folding cofactor (cofactor B) that greatly enhances the efficiency of alpha-tubulin folding in vitro. This enabled an integrated study of alpha- and beta-tubulin folding: we find that the pathways leading to the formation of native alpha- and beta-tubulin converge in that the folding of the alpha subunit requires the participation of cofactor complexes containing the beta subunit and vice versa. We also show that sequestration of native alpha-or beta-tubulins by complex formation with cofactors results in the destabilization and decay of the remaining free subunit. These data demonstrate that tubulin folding cofactors function by placing and/or maintaining alpha-and beta-tubulin polypeptides in an activated conformational state required for the formation of native alpha/beta heterodimers, and imply that each subunit provides information necessary for the proper folding of the other.

Contemporary use of antibiotics in 1089 adults presenting with acute lower respiratory tract illness in general practice in the U.K.: implications for developing management guidelines

Respiratory symptoms are the most common cause of general practitioner (GP) consultation, and hospital-based specialists are often called on to provide management guidelines, particularly in the area of antibiotic prescribing. The present authors have assessed factors associated with antibiotic use by 115 GPs when managing 1089 adults with an acute lower respiratory tract illness, including cough. They prescribed antibiotics to three-quarters of patients, but felt antibiotics to be definitely indicated in less than one-third of these cases and not needed in one-fifth. Univariate analysis revealed that antibiotics were prescribed more frequently by older GPs for older patients in the presence of underlying disease, discoloured sputum, shortness of breath, wheeze, fever, signs on chest examination, and 'other factors'. Multivariate logistic regression confirmed an independent effect for all these findings except for the presence of underlying disease, shortness of breath and wheeze. 'Other factors' included patient 'pressure' and social factors, and GP work pressure or prior experience with the patient. These factors were an important influence on prescribing, especially if the GP felt an antibiotic was not indicated. Amoxycillin was the first choice (58% of total) except where the patient had recently received antibiotics for the same illness. Broader spectrum antibiotics were used more commonly in patients with chronic lung disease, discoloured sputum, chest signs on examination and where the GP felt antibiotics were indicated. However, these antibiotics were also prescribed to 14% of previously well patients. General practitioners used a wide variety of terms to describe the illness with little consistency or structure. The decision concerning the use and choice of antibiotics and the confidence with which the GP makes that decision is a complex interaction between patient, doctor and disease, being affected not only by clinical features but also by the social and psychological elements of the presenting problem. Such issues need to be appreciated by hospital specialists when called on to advise on developing relevant guidelines for primary care.

Interleukin 10 prevents cytokine-induced disruption of T84 monolayer barrier integrity and limits chloride secretion

BACKGROUND & AIMS

The proinflammatory cytokine interferon gamma (IFN-gamma) disrupts epithelial barrier integrity and attenuates secretagogue-induced chloride secretion. This study tested the efficacy of the anti-inflammatory cytokine interleukin 10 (IL-10) in maintaining epithelial barrier and chloride secretory function in the presence of IFN-gamma.

METHODS

T84 epithelial cell monolayers were treated with IL-10, IFN-gamma, or IFN-gamma plus IL-10. Monolayer barrier integrity was assessed by measurements of electrical conductance, unidirectional mannitol and inulin fluxes, and tight junctional charge selectivity in Ussing chambers. Short-circuit current (Isc) was measured in response to carbachol and forskolin stimulation.

RESULTS

IL-10 attenuated the IFN-gamma-induced increase in electrical conductance and totally prevented the IFN-gamma-induced increase in mannitol and inulin fluxes. IL-10 did not prevent the IFN-gamma-induced abolishment of tight junctional charge selectivity but did attenuate the total increase in sodium and chloride permeability. IFN-gamma and IL-10 both separately reduced peak forskolin and carbachol-stimulated Isc. IL-10 pretreatment further enhanced the IFN-gamma-induced reduction in secretagogue-induced Isc.

CONCLUSIONS

In T84 epithelial monolayers, IL-10 maintains the size, but not the charge, selectivity of the epithelial tight junction in the presence of IFN-gamma. In addition, both IL-10 and IFN-gamma limit carbachol and forskolin-induced increase in Isc.