Electrical properties of dog tracheal epithelial cells grown in monolayer culture

Rock Inhibitor Y-27632 Enables Feeder-Free, Unlimited Expansion of Sus scrofa domesticus Swine Airway Stem Cells to Facilitate Respiratory Research

Current limitations in the efficacy of treatments for chronic respiratory disorders position them as prospective regenerative medicine therapeutic targets. A substantial barrier to these ambitions is that research requires large numbers of cells whose acquisition is hindered by the limited availability of human tissue samples leading to an overreliance on physiologically dissimilar rodents. The development of cell culture strategies for airway cells from large mammals will more effectively support the transition from basic research to clinical therapy. Using readily available porcine lungs, we isolated conducting airway tissue and subsequently a large number of porcine airway epithelial cells (pAECs) using a digestion and mechanical scraping technique. Cells were cultured in a variety of culture media formulations, both foetal bovine serum-containing and serum-free media, in air (21%) and physiological (2%) oxygen tension and in the presence and absence of Rho kinase inhibitor Y-27362 (RI). Cell number at isolation and subsequent population doublings were determined; cells were characterised during culture and following differentiation by immunofluorescence, histology, and IL-8 ELISA. Cells were positive for epithelial markers (pan-cytokeratin and E-cadherin) and negative for fibroblastic markers (vimentin and smooth muscle actin). Supplementation of cultures with Y-27632 allowed for unlimited expansion whilst sustaining an epithelial phenotype. Early passage pAECs readily produced differentiated air-liquid interface (ALI) cultures with a capacity for mucociliary differentiation retained after substantial expansion, strongly modulated by the culture condition applied. Primary pAECs will be a useful tool to further respiratory-oriented research whilst RI-expanded pAECs are a promising tool, particularly with further optimisation of culture conditions.

Early studies on the surface epithelium of mammalian airways

This article traces the beginnings of the various areas of physiological research on airway epithelium. First mentioned in 1600, it was not until 1834 that it was found to be ciliated. Goblet and basal cells were described in 1852, to be followed by ~10 other epithelial cell types (the most recent in 2018). It also contains nerve endings and resident leukocytes. Mucociliary clearance was documented in 1835, but the first studies on the ciliary beat cycle did not appear until 1890, and a definitive description was not published until 1981. It was established in 1932 that goblet cells in the cat trachea were unresponsive to cholinergic agents; but only since 1980 or so has any significant progress been made on what does cause them to degranulate. Active transfer of salts across epithelia creates local osmotic gradients that drive transepithelial water flows. Vectorial salt transport was first described for airway epithelium in 1968, and the associated volume flows were measured in 1981. Evidence that airway epithelium releases signaling molecules first appeared in 1981. Since then, scores of molecules have been identified. The pace of research in most areas increased dramatically after the development of confluent, polarized cultures of airway epithelium in the early 1980s.

Mechanisms of Meconium Passage: Cholinergic Stimulation of Electromechanical Coordination in the Fetal Colon

OBJECTIVE

Fetal gastrointestinal function develops in utero, with evidence of enhanced motility near-term. Although colonic passage of meconium in utero may be associated with fetal maturation or stress, little is known of the mechanisms potentiating motility. We assessed the effect of bethanechol, a cholinergic prokinetic agent, on colonic muscle muscular contractile and electromyogram (EMG) activity in the near-term ovine fetus.

METHODS

Near-term (130 days, n = 8) singleton ovine fetuses were chronically prepared with vascular catheters and three sets of miniature strain gauges and bipolar EMGs on the serosal surface of the transverse colon, left colic flexure, and distal colon. Following a 60-minute control period, fetuses received intravenous bethanechol (60 microg/kg, Low-Beth; 120 microg/kg, High-Beth) at 60 and 180 minutes. Colonic activity was recorded digitally and analyzed for short-duration (2<SHORT<15 seconds) and long-duration (15<LONG<120 seconds) strain gauge and EMG contractions. Data were expressed as means +/- SEM and analyzed using one-way analysis of variance (ANOVA) and paired t test.

RESULTS

During the control period, there was significantly greater SHORT versus LONG strain gauge contractions in all segments (P <.05). As compared to control values, Low-Beth and High-Beth significantly increased SHORT strain gauge contractions in the transverse colon (160 +/- 13 to 201 +/- 36 and 307 +/- 74 spikes/30 min, respectively, P <.05), although not in left colic flexure or distal colon. Bethanecol did not affect LONG strain gauge contractions. SHORT-EMG and LONG-EMG spike bursts did not change in response to bethanecol (280 +/- 20, 59 +/- 2 spikes/30 min, respectively).

CONCLUSION

Cholinergic stimulation of fetal sheep colonic activity at 0.9 gestation occurs in the transverse colon, but not the more distal left colic flexure or distal colon. The increased strain gauge, but not EMG activity, suggests that cholinergic stimulation improves electromechanical coordination in the fetal colon. We speculate that cholinergic-induced delivery of gastrointestinal contents to the distal colon evokes local contractile/expulsive mechanisms resulting in meconium passage.

Intracolonic Administration of the TRPA1 Agonist Allyl Isothiocyanate Stimulates Colonic Motility and Defecation in Conscious Dogs

BACKGROUND

The aim of the present study was to investigate the effects of the intracolonic transient receptor potential (TRP) A1 agonist allyl isothiocyanate (AITC) on colonic motility and defecation.

METHODS

The effects of AITC administered into the proximal colonic lumen on colonic motility and defecation were studied in neurally intact dogs equipped with strain-gauge force transducers on the colon, with or without various antagonists. Effects of intracolonic AITC were also studied in dogs with either transection/re-anastomosis (T/R) between the proximal and middle colon and complete extrinsic denervation of an ileocolonic segment.

RESULTS

AITC increased colonic motility and induced giant migrating contractions (GMCs) with defecations in 75% of experiments in neurally intact dogs. These effects were inhibited by atropine, hexamethonium, ondansetron, and HC-030031 but unaltered by capsazepine. In dogs with T/R, the increase in colonic motility was inhibited in the middle-distal colon. In dogs with extrinsic denervation, the increase in colonic motility in the distal colon was decreased.

CONCLUSIONS

Intracolonic AITC stimulates colonic motility and defecation via cholinergic, serotonergic, and TRPA1 pathways. Continuity of colonic enteric neurons plays an essential role in the intracolonic AITC-induced colonic motor response, while extrinsic nerves are important in occurrence and propagation of GMCs.

Role of the intraluminal contents and the continuity of intrinsic neurons in intracolonic capsaicin-induced contraction and defecation in dogs

PURPOSE

We, herein, examined the role of the intraluminal contents and continuity of colonic intrinsic neurons in intracolonic capsaicin-induced enhancement of colonic motility and defecation.

METHODS

Five beagle dogs were equipped with three strain gauge force transducers throughout the colon. The colonic contractile activity in response to intracolonic capsaicin was studied in intact dogs, dogs after colonic cleansing and dogs with transection/re-anastomosis (T/R) between the proximal and middle colon. The effects of intravenous yohimbine, a α2 adrenergic antagonist, on the colonic motility and defecation were also studied in the same models.

RESULTS

In intact dogs, capsaicin (10 mg) and yohimbine (2 mg/kg) immediately induced contractions throughout the colon, with defecation occurring in all experiments. In dogs after colonic cleansing and T/R, the capsaicin (10 mg)-induced enhancement of colonic motility was decreased in the middle and distal colon, and capsaicin-induced defecation was observed in 0-20 % of experiments (p < 0.05 compared to intact dogs). The effect of yohimbine (2 mg/kg) in inducing colonic contractions was unaltered after colonic cleansing and T/R; in contrast, yohimbine-induced defecation was not observed after colonic cleansing, but was unchanged after T/R.

CONCLUSIONS

The continuity of the colonic intrinsic nerves as well as the intraluminal contents appear to play an important role in the colonic motor response to intracolonic capsaicin.

Bovine oviductal monolayers cultured under three-dimension conditions secrete factors able to release spermatozoa adhering to the tubal reservoir in vitro

Different in vitro models have been developed to understand the interaction of gametes and embryos with the maternal reproductive tract. We recently showed that bovine oviductal monolayers three-dimensionally cultured in Gray's medium on collagen-coated microporous polycarbonate inserts under liquid-air interface conditions are well polarized, develop cilia, remain viable for at least 3 weeks postconfluence, and mantain the viability of bound spermatozoa significantly better than bidimensionally cultured monolayers. Herein, we used these culture conditions to understand whether: (1) spermatozoa adhering to three-dimensionally cultured oviductal monolayers can be released by heparin or penicillamine as previously shown with bidimensionally cultured oviductal monolayers and explants; and (2) media conditioned by three-dimensionally cultured oviductal monolayers were able to release spermatozoa adhering to oviductal explants. Findings demonstrated that (1) spermatozoa adhering to three-dimensionally cultured oviductal monolayers are readily released by heparin and penicillamine, (2) media conditioned by three-dimensionally cultured oviductal monolayers are able to release spermatozoa bound to oviductal explants, (3) do not depress sperm motility and viability, (4) they improve sperm kinetics, and (5) promote binding to the zona pellucida. In conclusion, in vitro data suggest that the release of spermatozoa adhering to the oviductal reservoir in vivo can be triggered by factors secreted by the oviduct itself that induce sperm capacitation.

Long-term viability and differentiation of bovine oviductal monolayers: bidimensional versus three-dimensional culture

Different in vitro models have been developed to study the interaction of gametes and embryos with the maternal tract. In cattle, the interaction of the oviduct with gametes and embryos have been classically studied using oviductal explants or monolayers (OMs). Explants are well differentiated but have to be used within 24 h after collection, whereas OMs can be used for a longer time after cell confluence but dedifferentiate during culture, losing cell polarity and ciliation. Herein, OMs were cultured either in M199 plus 10% fetal calf serum or in a semidefined culture medium (Gray's medium), in an immersed condition on collagen-coated coated microporous polyester or polycarbonate inserts under air-liquid interface conditions. The influence of culture conditions on long-term viability and differentiation of OMs was evaluated through scanning electron microscopy, localization of centrin and tubulin at the confocal laser scanning microscope, and assessment of maintenance of viability of sperm bound to OMs. Findings demonstrated that OMs cultured in an immersed condition with Gray's medium retain a better morphology, do not exhibit signs of crisis at least until 3 wks postconfluence, and maintain the viability of bound sperm significantly better than parallel OMs cultured in M199 plus 10% fetal calf serum. OM culture with Gray's medium in air-liquid interface conditions on porous inserts promotes cell polarity, ciliation, and maintenance of bound sperm viability at least until 3 wks postconfluence. In conclusion, oviduct culture in Gray's medium in an immersed or air-liquid condition allows long-term culture and, in the latter case, also ciliation of bovine OMs, and may represent in vitro systems that mimick more closely the biological processes modulated by the oviduct in vivo.

Chloride secretion by cultures of pig tracheal gland cells

Malfunction of airway submucosal glands contributes to the pathology of cystic fibrosis (CF), and cell cultures of CF human airway glands show defects in Cl(-) and water transport. Recently, a transgenic pig model of CF (the CF pig) has been developed. Accordingly, we have developed cell cultures of pig airway gland epithelium for use in investigating alterations in gland function in CF. Our cultures form tight junctions (as evidenced by high transepithelial electrical resistance) and show high levels of active anion secretion (measured as amiloride-insensitive short-circuit current). In agreement with recent results on human airway glands, neurohumoral agents that elevate intracellular Ca(2+) potently stimulated anion secretion, while elevation of cAMP was comparatively ineffective. Our cultures express lactoferrin and lysozyme (serous gland cell markers) and MUC5B (the main mucin of airway glands). They are, therefore, potentially useful in determining if CF-related alterations in anion transport result in altered secretion of serous cell antimicrobial agents or mucus.

Ion transport by pulmonary epithelia

The lung surface of air-breathing vertebrates is formed by a continuous epithelium that is covered by a fluid layer. In the airways, this epithelium is largely pseudostratified consisting of diverse cell types such as ciliated cells, goblet cells, and undifferentiated basal cells, whereas the alveolar epithelium consists of alveolar type I and alveolar type II cells. Regulation and maintenance of the volume and viscosity of the fluid layer covering the epithelium is one of the most important functions of the epithelial barrier that forms the outer surface area of the lungs. Therefore, the epithelial cells are equipped with a wide variety of ion transport proteins, among which Na⁺, Cl⁻, and K⁺ channels have been identified to play a role in the regulation of the fluid layer. Malfunctions of pulmonary epithelial ion transport processes and, thus, impairment of the liquid balance in our lungs is associated with severe diseases, such as cystic fibrosis and pulmonary oedema. Due to the important role of pulmonary epithelial ion transport processes for proper lung function, the present paper summarizes the recent findings about composition, function, and ion transport properties of the airway epithelium as well as of the alveolar epithelium.

Cystic fibrosis and the relationship between mucin and chloride secretion by cultures of human airway gland mucous cells

We investigated how cystic fibrosis (CF) alters the relationship between Cl(-) and mucin secretion in cultures of non-CF and CF human tracheobronchial gland mucous (HTGM and CFTGM, respectively) cells. Biochemical studies showed that HTMG cells secreted typical airway mucins, and immunohistochemical studies showed that these cells expressed MUC1, MUC4, MUC5B, MUC8, MUC13, MUC16, and MUC20. Effects of cumulative doses of methacholine (MCh), phenylephrine (Phe), isoproterenol (Iso), and ATP on mucin and Cl(-) secretion were studied on HTGM and CFTGM cultures. Baseline mucin secretion was not significantly altered in CFTGM cells, and the increases in mucin secretion induced by mediators were unaltered (Iso, Phe) or slightly decreased (MCh, ATP). Across mediators, there was no correlation between the maximal increases in Cl(-) secretion and mucin secretion. In HTGM cells, the Cl(-) channel blocker, diphenylamine-2-carboxylic acid, greatly inhibited Cl(-) secretion but did not alter mucin release. In HTGM cells, mediators (10(-5) M) increased mucin secretion in the rank order ATP > Phe = Iso > MCh. They increased Cl(-) secretion in the sequence ATP > MCh ≈ Iso > Phe. The responses in Cl(-) secretion to MCh, ATP, and Phe were unaltered by CF, but the response to Iso was greatly reduced. We conclude that mucin secretion by cultures of human tracheobronchial gland cells is independent of Cl(-) secretion, at baseline, and is unaltered in CF; that the ratio of Cl(-) secretion to mucus secretion varies markedly depending on mediator; and that secretions induced by stimulation of β-adrenergic receptors will be abnormally concentrated in CF.

CFTR and calcium-activated chloride channels in primary cultures of human airway gland cells of serous or mucous phenotype

Using cell culture models, we have investigated the relative importance of cystic fibrosis transmembrane conductance regulator (CFTR) and calcium-activated chloride channels (CaCC) in Cl secretion by mucous and serous cells of human airway glands. In transepithelial recordings in Ussing chambers, the CFTR inhibitor CFTR(inh)-172 abolished 60% of baseline Cl secretion in serous cells and 70% in mucous. Flufenamic acid (FFA), an inhibitor of CaCC, reduced baseline Cl secretion by ∼20% in both cell types. Methacholine and ATP stimulated Cl secretion in both cell types, which was largely blocked by treatment with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and partially by mucosal FFA or CFTR(inh)-172 with the exception of methacholine responses in mucous cells, which were not blocked by FFA and partially (∼60%) by CFTR(inh)-172. The effects of ionomycin on short-circuit current (I(sc)) were less than those of ATP or methacholine. Forskolin stimulated Cl secretion only if Cl in the mucosal medium was replaced by gluconate. In whole cell patch-clamp studies of single isolated cells, cAMP-induced Cl currents were ∼3-fold greater in serous than mucous cells. Ionomycin-induced Cl currents were 13 times (serous) or 26 times (mucous) greater than those generated by cAMP and were blocked by FFA. In serous cells, mRNA for transmembrane protein 16A (TMEM16A) was ∼10 times more abundant than mRNA for CFTR. In mucous cells it was ∼100 times more abundant. We conclude: 1) serous and mucous cells both make significant contributions to gland fluid secretion; 2) baseline Cl secretion in both cell types is mediated predominantly by CFTR, but CaCC becomes increasingly important after mediator-induced elevations of intracellular Ca; and 3) the high CaCC currents seen in patch-clamp studies and the high TMEM16A expression in intact polarized cells sheets are not reflected in transepithelial current recordings.

Characterization of special propulsive contractions during rectal evacuation in a canine model of intestinal extrinsic denervation and rectal transection

PURPOSE

The mechanism for the initiation of giant migrating contractions (GMCs) associated with defecation is not well known. The aim of this study was to describe the characteristics of special propulsive contractions (SPCs), such as GMCs, during evacuation in four experimental dog models, with emphasis on denervation.

MATERIALS AND METHODS

Twenty healthy dogs were used in this study, and they were divided into four groups, i.e., control (underwent force transducer implantation alone), denervation (underwent transection of the descending nerve fibers along the caudal mesenteric artery (CMA)), transection (underwent transection of the rectum, which corresponds to transection of the enteric nerve fibers), and denervation-plus-transection (underwent transection of the descending nerve fibers along the CMA and transection of the rectum). Colonic contractile activities were continuously recorded on a computer. Five force transducers were implanted at the serosal surfaces of the colon (C1-R). The consistency of dog feces was checked daily. The parameters of rectal relaxation (RR), defecation characteristics, and SPCs, such as motility index (MI), duration, and frequency, were measured.

RESULTS

In the control and denervation groups, GMCs were observed with evacuation, and RR occurred synchronously with the initiation of GMCs. On the other hand, in the transection and denervation-plus-transection groups, strong force contractions without RR occurred only during evacuation. The MI and duration of the transection and denervation-plus-transection groups were higher than those of other groups (p < 0.05). The frequency of SPCs was the highest in the denervation-plus-transection group.

CONCLUSIONS

In conclusion, the continuity of enteric nerves is necessary for the occurrence of GMCs and rectal relaxation (RR).

Cultures of human tracheal gland cells of mucous or serous phenotype

There are two main epithelial cell types in the secretory tubules of mammalian glands: serous and mucous. The former is believed to secrete predominantly water and antimicrobials, the latter mucins. Primary cultures of human airway gland epithelium have been available for almost 20 yr, but they are poorly differentiated and lack clear features of either serous or mucous cells. In this study, by varying growth supports and media, we have produced cultures from human airway glands that in terms of their ultrastructure and secretory products resemble either mucous or serous cells. Of four types of porous-bottomed insert tested, polycarbonate filters (Transwells) most strongly promoted the mucous phenotype. Coupled with the addition of epidermal growth factor (EGF), this growth support produced “mucous” cells that contained the large electron-lucent granules characteristic of native mucous cells, but lacked the small electron-dense granules characteristic of serous cells. Furthermore, they showed high levels of mucin secretion and low levels of release of lactoferrin and lysozyme (markers of native serous cells). By contrast, growth on polyethylene terephthalate filters (Cyclopore) in medium lacking EGF produced “serous” cells in which small electron-dense granules replaced the electron-lucent ones, and the cells had high levels of lactoferrin and lysozyme but low levels of mucins. Measurements of transepithelial resistance and short-circuit current showed that both “serous” and “mucous” cell cultures possessed tight junctions, had become polarized, and were actively secreting Cl.

In vitro susceptibility to rhinovirus infection is greater for bronchial than for nasal airway epithelial cells in human subjects

BACKGROUND

Human rhinoviruses (HRVs) characteristically cause upper respiratory tract infection, but they also infect the lower airways, causing acute bronchitis and exacerbating asthma.

OBJECTIVE

Our purpose was to study ex vivo the differences in the response to HRV infection of nasal and bronchial epithelial cultures from the same healthy and asthmatic individuals using conditions favoring development of fully differentiated, pseudostratified mucociliary epithelium.

METHODS

Cells from the inferior turbinates and bronchial tree of 5 healthy and 6 asthmatic individuals were cultured at an air-liquid interface. Cultures were infected with HRV-16, and after 48 hours, the degree of infection was measured.

RESULTS

Baseline median transepithelial resistance was lower in human bronchial epithelial (HBE) cell cultures than in human nasal epithelial (HNE) cell cultures (195 Omega.cm2 [95% CI, 164-252] vs 366 Omega.cm2 [95% CI, 234-408], respectively; P < .01). Virus replicated more easily in HBE cells than in HNE cells based on virus shedding in apical wash (log tissue culture infective dose of 50%/0.1 mL = 2.0 [95% CI, 1.0-2.5] vs 0.5 [95% CI, 0.5-1.5], P < .01) and on a 20- to 30-fold greater viral load and number of infected cells in HBE cell cultures than in HNE cell cultures. The increases in expression of RANTES and double-stranded RNA-dependent protein kinase were greater in HBE cell cultures than in HNE cell cultures, as were the concentrations of IL-8, IL-1alpha, RANTES, and IP-10 in basolateral medium. However, no significant differences between asthmatic and healthy subjects (including IFN-beta1 expression) were found.

CONCLUSIONS

Differentiated nasal epithelial cells might have mechanisms of increased resistance to rhinovirus infection compared with bronchial epithelial cells. We could not confirm previous reports of increased susceptibility to HRV infection in epithelial cells from asthmatic subjects.

Hormonal and purinergic stimulation of bicarbonate secretion in oviducts of rhesus monkey

Because an increase in the HCO(3)(-) concentration of oviductal liquid at midcycle is believed to markedly enhance fertility, we have studied active secretion of HCO(3)(-) across highly differentiated cultures of monkey oviductal epithelium. Cultured cell sheets were mounted in Ussing chambers and bathed in medium containing 25 mM HCO(3)(-). Purinergic agents potently stimulated short-circuit current (I(sc)) with an initial transient response declining within approximately 2 min to a sustained response. The potency sequence of ATP approximately UTP > ADP >> AMP suggested that the I(sc) response was mediated mainly by P2Y(2) receptors. Acetazolamide, an inhibitor of carbonic anhydrase, had little or no effect on baseline I(sc) or the transient response to ATP but abolished the sustained response to ATP. Similar results were obtained on sheets of native epithelium. In pH-stat experiments, the abluminal medium of cell cultures was bathed in HCO(3)(-)-CO(2) medium, and the pH of the unbuffered luminal medium was maintained at approximately 7.4 by addition of strong acid or base. ATP stimulated base secretion, and this was inhibited by acetazolamide. Furthermore, these changes in secretion of base were in good quantitative agreement with the I(sc) responses. When phenol red (an estrogen) was removed from the culture medium, ATP-dependent HCO(3)(-) secretion was markedly reduced but could be restored by treatment with estradiol. Estrogens also markedly increased ciliation of the cultures. These results suggest that the midcycle increase in the HCO(3)(-) concentration of oviductal liquid may be mediated by the effects of estradiol on purinergic pathways or on ATP secretion.

Fluid Transport Across Airway Epithelia

Active ion transport across the surface epithelium of dog trachea results in fluid transport. The direction and amount of fluid transported may depend on a balance between active chloride secretion and active sodium absorption. In contrast, fluid movement across submucosal gland epithelium does not seem to depend on active salt transport. Instead, water may be drawn into the duct lumen by simple osmosis after the release of the osmotically active contents of secretory granules. Cell culture may provide a means of studying the secretory properties of the individual cell types of airway epithelia. We have produced primary monolayer cultures of cells from dog tracheal epithelium which retain the differentiated salt and water transport of the original tissue.

Gastrointestinal motility after digestive surgery

Gastrointestinal (GI) motility dysfunction is a common complication of any abdominal surgical procedure. During fasting, the upper GI tract undergoes a cyclic change in motor activity, called the interdigestive migrating motor contraction (IMC). The IMC is divided into four phases, with phase III having the most characteristic activity. After digestive surgery, GI motility dysfunction shows a lack of a fed response, less phase II activity, more frequent phase III activity of the IMC, and some phase III activity migrating orally. Postoperative symptoms have been related to motor disturbances, such as interrupted or retrograde phase III or low postprandial activity. The causes of GI disorder are autonomic nervous dysfunction and GI hormone disruptions. The administration of a motilin agonist can induce earlier phase III contractions in the stomach after pancreatoduodenectomy. For nervous dysfunction, an inhibitory sympathetic reflux is likely to be important in postoperative motility disorders. Until recently, treatment for gut dysmotility has consisted of nasogastric suction, intravenous fluids, and observation; however, more effective treatment methods are being reported. Recent discoveries have the potential to decrease postoperative gut dysmotility remarkably after surgery.

Role of alpha-2 adrenoceptors in regulation of giant migrating contractions and defecation in conscious dogs

The aim was to investigate the effects of alpha(2)-adrenoceptor antagonist yohimbine on colonic motility and defecation. The effects of yohimbine (0.5, 1.0, and 3.0 mg/kg) on colonic motility and defecation were studied in neurally intact dogs (N=6), dogs with extrinsic denervation of the ileocolon (N=4), and dogs with enterically isolated ileocolnic loops (N=5) equipped with strain gauge force transducers on the ileocolon. The effects of yohimbine on colonic motility and defecation were also studied in the presence of various antagonists (atropine, hexamethonium, ondansetron, FK224, and naloxone). Yohimbine evoked giant migrating contractions and defecation in a dose-independent manner in neurally intact dogs. These stimulatory effects of yohimbine were abolished by atropine and hexamethonium. In dogs with extrinsic denervation, yohimbine induced giant migrating contractions in the colon but did not stimulate defecation. In dogs with ileocolonic loops, yohimbine induced colonic motor complexes but not giant migrating contractions in the enterically isolated colon. These results indicate that alpha(2)-adrenoceptors in the peripheral nervous system regulate giant migrating contractions by controlling the release of acetylcholine, while those in the central nervous system must be important in the regulation of defecation.

Differentiated structure and function of primary cultures of monkey oviductal epithelium

We have established well-differentiated, polarized cultures of monkey oviductal epithelium. Oviductal epithelial cells were isolated by protease digestion and plated on collagen-coated, porous cell culture inserts. About 5 d after plating, cells developed detectable transepithelial electrical resistance of up to 2000 Omega.cm(2) (an index of tight junction formation) and transepithelial voltages of up to 20 mV (an index of vectorial transepithelial ion transport). Measurements of short-circuit current in Ussing chambers indicated that active secretion of Cl was the major transepithelial active ion transport process, and that this was stimulated by elevation of either cAMP or Ca(i). Furthermore, estimates of the volume of mucosal liquid were consistent with Cl secretion mediating fluid secretion. Various microscopical methods showed that the cultures were densely ciliated and contained mature secretory cells. Transport across the oviductal epithelium determines the composition of the oviductal fluid, and the study of the relevant transport processes will be greatly enhanced by well-differentiated cultures of oviductal epithelium of the kind established here.

Neural gastrointestinal electrical stimulation enhances colonic motility in a chronic canine model of delayed colonic transit

Neural gastrointestinal electrical stimulation (NGES) induces sequential contractions and enhances emptying in acute canine gastric and colonic models. This study was set to determine (i) the effect of NGES in a chronic canine model of delayed colonic transit and (ii) possible mechanism of action. Four pairs of electrodes were implanted in the distal colon of nine mongrel dogs. Delayed colonic transit was induced by diphenoxylate/atropine and alosetron. Transit was fluoroscopically determined by the rate of evacuation of radiopaque markers, and was tested twice in each dog, in random order, on and off stimulation. Two stimulation sequences, separated by 1 min, were delivered twice a day via exteriorized electrodes. Colonic manometry during stimulation was performed before and after intravenous (i.v.) injection of 1 mg of atropine. Complete evacuation of all markers was significantly shortened by NGES, from 4 days to 2 days, interquartile range 3-4 days vs 2-3 days, respectively, P = 0.016. NGES induced strong sequential contractions that were significantly diminished by atropine: 190.0 +/- 14.0 mmHg vs 48.7 +/- 19.4 mmHg, respectively (P < 0.001). NGES induces strong sequential colonic contractions and significantly accelerates movement of content in a canine model of delayed colonic transit. The effect is atropine sensitive.

Expansion of cultures of human tracheal epithelium with maintenance of differentiated structure and function

We have developed a technique for expanding primary cultures of human tracheal epithelium while minimizing loss of differentiated structure and function. Cells were seeded at 2 x 10(4) cells/cm2 into T75 flasks and trypsinized when approximately 80% confluent. The dispersed cells were then passaged at the same plating density into further T75 flasks or seeded at 5 x 10(5) cells/cm2 on porous-bottomed inserts and maintained with an air-interface. Differentiation of cells on inserts was assessed from transepithelial electrical resistance (an index of tight junction formation), short-circuit current (an index of transepithelial salt transport), cell numbers, total cell protein, and histology. Unpassaged cells (P0) and cells passaged once (P1) took about a week to become 80% confluent on T75 flasks, with 10-fold and 5-fold increases in cell numbers, respectively. Confluence was achieved in approximately 3 days following plating to inserts. Functionally and structurally, P1 and P2 cells (cells passaged twice) were little different from P0 cells. Thus, within a little over 2 weeks, the numbers of confluent cell sheets can be increased 50-fold with minimal change in function. However, there was a marked decline in differentiation by cells passaged three times (P3), and not all cell preparations could be taken to P4 (cells passaged four times).

Secretion of lactoferrin and lysozyme by cultures of human airway epithelium

Lactoferrin and lysozyme are important antimicrobial compounds of airway surface liquid, derived predominantly from serous cells of submucosal glands but also from surface epithelium. Here we compared release of these compounds from the following human cell cultures: primary cultures of tracheal epithelium (HTE), Calu-3 cells (a lung adenocarcinoma cell line frequently used as a model of serous gland cells), 16HBE14o- cells (an SV40 transformed line from airway surface epithelium), T84 cells (a colon carcinoma cell line), and human foreskin fibroblasts (HFF). For lysozyme, baseline secretory rates were in the order Calu-3 > 16HBE14o- > HTE ≈ T84 > HFF = 0; for lactoferrin, the only cell type showing measurable release was HTE; for mucus, HTE > Calu-3 > 16HBE14o- ≈ T84 > HFF = 0. A wide variety of neurohumoral agents and inflammatory stimuli was without effect on lactoferrin and lysozyme release from HTE or Calu-3 cells, although forskolin did stimulate secretion of water and lysozyme from Calu-3 cells. However, the concentration of lysozyme in the forskolin-induced secretions was much less than in airway gland secretions. Thus our data cast doubt on the utility of Calu-3 cells as a model of airway serous gland cells but do suggest that HTE could prove highly suitable for studies of mucin synthesis and release.

Resistance of differentiated human airway epithelium to infection by rhinovirus

Virtually all in vitro studies of the effects of rhinovirus on human airway epithelium have used cells grown under conditions known to produce low levels of differentiation. The relevance of the results to native epithelium is questionable. Here we grew primary cultures of human tracheal or nasal epithelium under three conditions. One condition produced pseudostratified, mucociliary cells virtually indistinguishable from native epithelium. The other two conditions produced undifferentiated squamous cells lacking cilia. Cells were infected for 6 h with rhinovirus-16. After a 24-h incubation period, we determined levels of viral RNA in the cells, numbers of infectious viral particles released in the mucosal medium, expression of a variety of epithelial cytokines and other proteins, release of IL-6 and IL-8, and transepithelial electrical resistance and voltage. After infection, levels of viral RNA in the poorly differentiated cells were 30 or 130 times those in the differentiated. Furthermore, expression of mRNA for inflammatory cytokines, release of infectious particles, and release of IL-6 and IL-8 were closely correlated with the degree of viral infection. Thus well-differentiated cells are much more resistant to viral infection and its functional consequences than are poorly differentiated cells from the same source.

Stimulatory action of itopride hydrochloride on colonic motor activity in vitro and in vivo

We investigated the effects of itopride hydrochloride (itopride, N-[4-[2-(dimethylamino)ethoxy]benzyl]-3,4-dimethoxybenzamide hydrochloride), a gastroprokinetic agent, on the colonic motor activity in vitro and in vivo, in comparison with benzamides, cisapride hydrate (cisapride), and mosapride citrate (mosapride). Itopride stimulated both peristaltic and segmental motility induced by applying intraluminal pressure to the isolated guinea pig colon. Although cisapride and mosapride enhanced the segmental motility, they markedly reduced the peristaltic motility. In conscious dogs with implanted strain gauge force transducers, itopride stimulated contractile activity in the gastrointestinal tract from the stomach to the colon. Cisapride stimulated contractile activity in the gastric antrum, ileum, and ascending colon. Mosapride stimulated contractile activity only in the gastric antrum and ileum. In guinea pigs and rats, itopride accelerated colonic luminal transit. On the other hand, cisapride and mosapride failed to enhance colonic transit. These results demonstrate that itopride has a stimulatory action on colonic peristalsis, propelling colonic luminal contents, different from that of cisapride and mosapride. Therefore, itopride may be a useful drug for the treatment of functional bowel disorders such as functional constipation.

Effects of media on differentiation of cultured human tracheal epithelium

The purpose of the this study was to find media that supported high levels of differentiation in primary cultures of human tracheal epithelium. We tested six previously described, partially defined media and three nondefined media. Cells were grown with an air interface on porous-bottomed inserts, and differentiation was assessed from electrophysiological properties, levels of total protein and deoxyribonucleic acid, and histology. In all media, cells polarized and developed tight junctions, as assessed from transepithelial electrical resistance and were better differentiated at 14 d after plating than at 7 d. The partially defined media described previously by Gray et al. (Am. J. Respir. Cell. Mol. Biol. 14:104-112; 1996) and Matsui et al. (J. Clin. Invest. 102:1125-1131; 1998) and an undefined medium containing Ultroser G serum substitute produced the most highly differentiated epithelial cells, as revealed by a high short-circuit current (I(sc)) and a ciliated, pseudostratified appearance. In other media, cells tended to be either squamous or stratified squamous, with I(sc) levels <25% of those obtained with the three optimal media. Though no key factor in the composition of the partially defined media could be identified, two of the four media with high concentrations of retinoic acid produced good differentiation. In contrast, the two media with the lowest [Ca] (0.11 mM) produced poorly differentiated cells, as did the two partially defined media with low or no retinoic acid concentration.

Acid secretion and proton conductance in human airway epithelium

Acid secretion and proton conductive pathways across primary human airway surface epithelial cultures were investigated with the pH stat method in Ussing chambers and by single cell patch clamping. Cultures showed a basal proton secretion of 0.17 +/- 0.04 micromol.h(-1).cm(-2), and mucosal pH equilibrated at 6.85 +/- 0.26. Addition of histamine or ATP to the mucosal medium increased proton secretion by 0.27 +/- 0.09 and 0.24 +/- 0.09 micromol.h(-1).cm(-2), respectively. Addition of mast cells to the mucosal medium of airway cultures similarly activated proton secretion. Stimulated proton secretion was similar in cultures bathed mucosally with either NaCl Ringer or ion-free mannitol solutions. Proton secretion was potently blocked by mucosal ZnCl(2) and was unaffected by mucosal bafilomycin A(1), Sch-28080, or ouabain. Mucosal amiloride blocked proton secretion in tissues that showed large amiloride-sensitive potentials. Proton secretion was sensitive to the application of transepithelial current and showed outward rectification. In whole cell patch-clamp recordings a strongly outward-rectifying, zinc-sensitive, depolarization-activated proton conductance was identified with an average chord conductance of 9.2 +/- 3.8 pS/pF (at 0 mV and a pH 5.3-to-pH 7.3 gradient). We suggest that inflammatory processes activate proton secretion by the airway epithelium and acidify the airway surface liquid.

Expression of discoidin domain receptor 1 tyrosine kinase on the human bronchial epithelium

Discoidin domain receptor 1 (DDR1) tyrosine kinases constitute a novel family of receptors characterized by a unique structure in the ectodomain (discoidin-I domain). The DDR1 ligand is the extracellular matrix protein collagen. To identify receptor tyrosine kinases (RTKs) involved in control of growth and differentiation of human bronchial epithelial (HBE) cells, a polymerase chain reaction-based search for RTKs in HBE cells was performed. DDR1 was the most abundant clone identified. Northern analysis detected a 3.6 kb DDR1 messenger ribonucleic acid (mRNA) expressed in HBE cells and transformed HBE lines, BET-1A and BEAS-2B. In addition, fluorescence-activated cell sorter (FACS) analyses using an anti-DDR1 antibody showed that DDR1 was expressed on HBE cells and two HBE lines. Immunohistochemical staining using human bronchial tissue demonstrated that DDR1 was mainly expressed at the basolateral cell surface of the bronchial epithelium. Furthermore, immunostaining of type IV collagen, a major component of the basement membrane, clearly showed that the basement membrane was closely attached to the basal surface of the bronchial epithelium. Since collagen binds to and activates discoidin domain receptor 1 tyrosine kinase, colocalization of discoidin domain receptor 1 and its ligand type IV collagen demonstrates a potential interaction of discoidin domain receptor 1 on the bronchial epithelium with type IV collagen. Further study of this interaction may define the functional significance of the collagen-discoidin domain receptor 1 signalling pathway in health and in disease.

Syntaxin 1A is expressed in airway epithelial cells, where it modulates CFTR Cl(-) currents

The CFTR Cl(-) channel controls salt and water transport across epithelial tissues. Previously, we showed that CFTR-mediated Cl(-) currents in the Xenopus oocyte expression system are inhibited by syntaxin 1A, a component of the membrane trafficking machinery. This negative modulation of CFTR function can be reversed by soluble syntaxin 1A peptides and by the syntaxin 1A binding protein, Munc-18. In the present study, we determined whether syntaxin 1A is expressed in native epithelial tissues that normally express CFTR and whether it modulates CFTR currents in these tissues. Using immunoblotting and immunofluorescence, we observed syntaxin 1A in native gut and airway epithelial tissues and showed that epithelial cells from these tissues express syntaxin 1A at >10-fold molar excess over CFTR. Syntaxin 1A is seen near the apical cell surfaces of human bronchial airway epithelium. Reagents that disrupt the CFTR-syntaxin 1A interaction, including soluble syntaxin 1A cytosolic domain and recombinant Munc-18, augmented cAMP-dependent CFTR Cl(-) currents by more than 2- to 4-fold in mouse tracheal epithelial cells and cells derived from human nasal polyps, but these reagents did not affect CaMK II-activated Cl(-) currents in these cells.

Gastrointestinal peristalsis: joint action of enteric nerves, smooth muscle, and interstitial cells of Cajal

Peristalsis is a propulsive motor pattern orchestrated by neuronal excitation and inhibition in cooperation with intrinsic muscular control mechanisms, including those residing in interstitial cells of Cajal (ICC). Interstitial cells of Cajal form a network of cells in which electrical slow waves originate and then propagate into the musculature initiating rhythmic contractile activity upon excitaton by enteric nerves. Interstitial cells of Cajal have now been isolated and their intrinsic properties reveal the presence of rhythmic inward currents not found in smooth muscle cells. In tissues where classical slow waves are not present, enteric cholinergic excitation will evoke slow wave-like activity that forces action potentials to occur in a rhythmic manner. Intrinsic and induced slow wave activity directs many of the peristaltic motor patterns in the gut.

Quantitation of bacterial adherence by image analysis

In studies of the adherence of pathogenic bacteria to host eukaryotic cells in vitro, the counting of the bacteria is often challenging, especially if many experiments are involved. We developed a method to use digital imaging and computer-aided recognition for the quantitation of bacteria attached to cultured cells. We employed an immunocytochemical method to stain the bacteria and leave the hosts cells relatively unstained. We describe this method for use with five species of bacteria, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Chlamydia pneumoniae. To demonstrate an application of this method, we studied the attachment of H. influenzae and S. pneumoniae to target epithelial cell lines derived from the respiratory tract.

Colonic motility in man: features in normal subjects and in patients with chronic idiopathic constipation

The human colon is still a relatively unknown viscus, especially concerning its motor activity. However, in recent years, techniques have been perfected that allow a better understanding of colonic motility, especially through prolonged recording periods. In this way, it has been demonstrated that the viscus contracts according to a circadian trend, is responsive to physiological stimuli (meals, sleep), and features high amplitude, propulsive contractions that are part of the complex dynamic of the defecatory process. These physiological properties and their alterations in patients with chronic idiopathic constipation are reviewed in this article.

Adherence of Streptococcus pneumoniae to respiratory epithelial cells is inhibited by sialylated oligosaccharides

To study carbohydrate-mediated adherence of Streptococcus pneumoniae to the human airway, we measured binding of live S. pneumoniae organisms to a cultured cell line derived from the lining of the conjunctiva and to primary monolayers of human bronchial epithelial cells in the presence and absence of oligosaccharide inhibitors. Both encapsulated and nonencapsulated strains of S. pneumoniae grown to mid-logarithmic phase in suspension culture adhered to cultured primary respiratory epithelial cells and the conjunctival cell line. Adherence of nine clinically prevalent S. pneumoniae capsular types studied was inhibited preferentially by sialylated oligosaccharides that terminate with the disaccharide NeuAc alpha2-3(or 6)Galbeta1. Adherence of some strains also was weakly inhibited by oligosaccharides that terminate with lactosamine (Galbeta1-4GlcNAcbeta1). When sialylated oligosaccharides were covalently coupled to human serum albumin at a density of approximately 20 oligosaccharides per molecule of protein, the molar inhibitory potency of the oligosaccharide inhibitor was enhanced 500-fold. The above-mentioned experiments reveal a previously unreported dependence upon sialylated carbohydrate ligands for adherence of S. pneumoniae to human upper airway epithelial cells. Enhanced inhibitory potencies of polyvalent over monovalent forms of oligosaccharide inhibitors of adherence suggest that the putative adhesin(s) that recognizes the structure NeuAc alpha2-3(or 6)Galbeta1 is arranged on the bacterial surface in such a manner that it may be cross-linked by oligosaccharides covalently linked to human serum albumin.

Role of macrophage-stimulating protein and its receptor, RON tyrosine kinase, in ciliary motility

Macrophage-stimulating protein (MSP) is an 80-kD serum protein with homology to hepatocyte growth factor (HGF). Its receptor, RON tyrosine kinase, is a new member of the HGF receptor family. The MSP-RON signaling pathway has been implicated in the functional regulation of mononuclear phagocytes. However, the function of this pathway in other types of cells has not been elucidated. Here we show that in contrast to the HGF receptor, which was expressed at the basolateral surface, RON was localized at the apical surface of ciliated epithelia in the airways and oviduct. In addition, MSP was found in the bronchoalveolar space at biologically significant concentrations. MSP bound to RON on normal human bronchial epithelial cells with a high affinity (Kd = 0.5 nM) and induced autophosphorylation of RON. Activation of RON by MSP led to a significant increase in ciliary beat frequency of human nasal cilia. These findings indicate that the ciliated epithelium of the mucociliary transport apparatus is a novel target of MSP. Ciliary motility is critical for mucociliary transport. Our findings suggest that the MSP-RON signaling pathway is a novel regulatory system of mucociliary function and might be involved in the host defense and fertilization.

Influence of ileal pouch capacity and anal sphincteric function on the clinical outcome after ileal pouch-anal anastomosis

This study was designed to determine the influence of ileal pouch capacity and anal sphincteric function on the clinical outcome after ileal pouch-anal anastomosis. A total of 24 patients who had undergone ileal pouch-anal anastomosis (J pouch) for ulcerative colitis were studied. The 24-hour stool frequency was found to be inversely correlated with the sensitivity threshold volume (STV), maximal tolerance volume (MTV), and distensibility, but was independent of the maximal resting pressure and maximal squeeze pressure. Patients experiencing nocturnal fecal incontinence had maximal resting pressures that were significantly lower than those of nocturnally continent patients. Among the patients with fecal incontinence, those with frequent soiling had lower resting pressures, STV, and distensibility than the patients with intermittent spotting. In addition, the STV in patients needing nocturnal evacuation were lower than those of patients who did not evacuate after falling asleep. The conclusions are as follows. Both stool frequency and the need for nocturnal pouch evacuation correlated directly with pouch volume. Anal incontinence was more common in patients with low internal sphincteric function. In addition, frequent and gross nocturnal incontinent patients demonstrate a worse function in both the anal sphincter and reservoir than those with intermittent spotting.

Method for the growth of equine airway epithelial cells in culture

A serum-free cell culture method was developed for equine tracheal epithelial cells which allowed the growth and characterisation of the phenotypical properties of this cell type. Several variables influenced the efficacy of the attachment and growth of the isolated cells. Serum and a collagen matrix were essential components for efficient cell attachment. Once attachment had occurred, cell growth was enhanced by a serum-free medium containing bovine pituitary extract, retinoic acid, insulin, hydrocortisone, transferrin, epidermal growth factor, adrenaline and triiodothyronine. The mean time taken for the cells to grow to confluency varied from 12.6 to 28.0 days, depending on the medium used. Collagen matrix was essential to aid the proliferation of the cells.

Antiproteases attenuate the release of neutrophil chemotactic activity from bronchial epithelial cells induced by smoke

The released neutrophil chemotactic activity (NCA) from bronchial epithelial cells (BECs) in response to smoke extract was evaluated by reverse-phase, high-performance liquid chromatography (RP-HPLC) and the involvement of proteolytic activity was assessed for the release of NCA from BECs. Smoke extract stimulated the release of NCA (55.3 +/- 5.2 vs. 17.3 +/- 4.1 cells per high-power field [HPF], p < .001). The released activity determined by RP-HPLC analysis was 15-hydroxyeicosatetraenoic acid and leukotriene B4. Several structurally and functionally different serine protease inhibitors, including alpha-1-protease inhibitor (alpha-1-PI), chloromethyl ketone (CK) derivatives, N-tosyl-L-lysine CK (TLCK), methoxysuccinyl-Ala-Ala-Pro-Val CK (SPCK), N-alpha-tosyl-L-phenylalanine CK (TPCK), and N-alpha-p-tosyl-L-arginine methyl ester hydrochloride (TAME), attenuated the release of NCA (P < .01) in a dose-dependent fashion. Leupeptin, a cysteine protease inhibitor, has only a small effect on the release of NCA (p < .05), and phosphoramidon, a neutral endopeptidase inhibitor, had no effect. The measurement of proteolytic enzyme activity using synthetic substrate S-2288 revealed that smoke extract significantly (p < .05) augmented the serine protease activity in BEC layers. Culture supernatant fluids and cell lysates of BECs in response to smoke extract solubilized 14C-labeled casein. These results suggest that BECs may release lipoxygenase-derived NCA in response to smoke extract and that the release of NCA may involve the activation of proteolytic activity of BECs which was inhibited by serine protease inhibitors.

Cationic proteins increase the permeability of cultured rabbit tracheal epithelial cells: modification by heparin and extracellular calcium

Airway inflammation is a consistent finding in asthma, and increased amounts of eosinophil-derived cationic proteins are present in bronchoalveolar lavage fluid from asthmatic subjects. Tracheal instillation of a variety of naturally occurring and synthetic cationic proteins has been shown to induce airway hyperresponsiveness in animal models. Cationic proteins may alter the barrier function of airway epithelium, allowing increased access of agonists to underlying nerves and airway smooth muscle. To examine the effect of cationic proteins on airway epithelial cell function, rabbit tracheal epithelial cells were isolated and cultured on collagen-coated filter membranes. Both apical and basolateral exposure of the cell cultures to poly-L-lysine and poly-L-arginine decreased transepithelial electrical resistance (Rt) over 60 min. There were no discernable light microscopic changes in the morphology of the cultures at 60 min after poly-L-lysine exposure, but permeability to mannitol was increased compared to controls. Evidence for the critical role of cationic charge included the following observations: (1) Poly-L-aspartate, an anionic polyamino acid, had no significant effect on Rt, and (2) the addition of heparin prior to the addition of poly-L-lysine blocked the reduction in Rt. Furthermore, when applied after poly-L-lysine addition, heparin reversed the decrease in Rt in a time-dependent fashion. Increasing the [Ca2+] in the medium from 1 to 10 mM resulted in significant attenuation of the response to polycation addition. These findings suggest that cationic proteins significantly alter the barrier properties of airway epithelium and that cationic charge is a crucial factor. This alteration is not an "all or none" phenomenon, since subsequent addition of heparin resulted in a reversal of the effect. While the precise mechanisms responsible for these observations remain to be elucidated, cationic proteins may be modifying the interaction of extracellular calcium with tight junctions thereby resulting in increased permeability. The barrier function of the epithelium may be perturbed in asthma and a variety of other airway diseases through the presence of cationic proteins derived from inflammatory cells within the airway lumen and/or the subepithelium.

Effect of celiac and superior mesenteric ganglionectomy on fasted canine colonic motor activity

The role played by extrinsic nerves in colonic motor activity and motor coordination between the small intestine and the colon in the fasting state was investigated in a canine model. To evaluate motor activity before and after celiac and superior mesenteric ganglionectomy (CSMG), seven strain gauge force transducers were implanted in the small and large bowels of five dogs. No significant differences were observed in the frequency, duration, cycle, or migration time of bursts of contractions from the colon (BCC), or in the duration of the quiescent state before and after CSMG. When small intestinal phase III activity reached the ileocecal junction before and after CSMG, a characteristic contractile pattern, namely, small intestinal phase III activity followed by BCC, was observed at the ileocecal junction. Before and after CSMG, 84% and 83% of the small intestinal phase III activity, respectively, was transmitted to the colon as BCC after reaching the ileocecal junction. However, only 19% and 18% of BCC before and after CSMG, respectively, followed small intestinal phase III activity. These results led us to conclude that the extrinsic nerves exert little effect on fasting colonic motor activity and motor transmission from the small intestine to the colon.

Human colonic motility: physiological aspects

From the point of view of its motor activity, the human colon is probably the least understood of the abdominal hollow viscera. This is due to several facts: a) its proximal portions are relatively inaccessible due to anatomical reasons; b) there is no reliable animal model due to the considerable anatomic-physiological differences among mammals. For instance, most deductions about human colonic motor activity have been drawn from experiences in cats and dogs, in which the colon displays a cecum which is almost atrophic, and the viscus is featureless and C-shaped, without the haustrations and the sharp angulations seen in man, c) the wide fluctuations of motility in the daily time course of the same individual makes the interpretation of many studies difficult, especially considering the fact that, until recently, most of the studies on human colonic motility have been conducted for relatively short (30-180 min) recording periods. Recently, however, techniques that allow recording from the proximal portions of the human colon have been developed, and prolonged (24 h or more) observations of myoelectrical and contractile events have been achieved, thus improving our knowledge of the normal physiologic properties of the viscus. These informations have furthermore been integrated and confirmed by scintigraphic techniques (less invasive), that allow the measurement of intracolonic flow activity. The purpose of the present paper is to review the physiological aspects of colonic motility in man, quoting animal studies where human ones are lacking. We will briefly introduce some basic concepts, then a more detailed description of the main topic will follow.

Distension-stimulated propagated contractions in human colon

To investigate the mechanisms for elicitation of peristaltic activity in the human colon, we studied the effect of balloon distension of the transverse, descending, and sigmoid colon and the rectum. Fifteen healthy subjects were studied by means of a colonoscopically positioned probe carrying a 5-cm latex balloon. After positioning of the probe, stepwise distension was performed for each colonic segment (transverse, descending, sigmoid, rectum), and the onset of large (> 50 mm Hg) and small (< 50 mm Hg) propagated waves was observed. Analysis of the tracings showed: (1) In 8/15 subjects (53.3%), balloon distension elicited propagated contractions, but these contractions were qualitatively different from the spontaneously occurring high-amplitude propagated contractions previously found to occur in association with defecation. Therefore, intraluminal distension is probably not the cause of defecation-associated high-amplitude propagated contractions. (2) Pain reports were poorly correlated with propagated contractions elicited by balloon distension, suggesting that these contractions are not the cause of the pain produced by balloon distension. (3) The transverse colon shows lower pressures, fewer pain reports, and fewer large propagated contractions in response to balloon distension as compared to the descending and the sigmoid colon.

Influenza virus induces expression of antioxidant genes in human epithelial cells

Influenza infections cause airway epithelial inflammation and oxidant-mediated damage. In this setting, cellular antioxidant enzymes may protect airway epithelial cells against damage resulting from toxic oxygen radicals produced by activated leukocytes. Therefore, we tested the effect of influenza virus infection, as well as exposed to human recombinant interferon-gamma (IFN-gamma), on gene expression for the antioxidant enzymes manganese superoxide dismutase (MnSOD), copper/zinc superoxide dismutase (Cu/ZnSOD), indoleamine 2,3-dioxygenase (IDO), and catalase in primary cultures of human airway epithelial cells. In these cells, both viral infection and IFN-gamma increased MnSOD and IDO mRNAs. In contrast, neither viral infection nor IFN-gamma affected Cu/ZnSOD gene expression, and both viral infection and IFN-gamma decreased catalase gene expression. The differential effects of viral infection on antioxidant gene expression and their further amplification by IFN-gamma are likely to be important protective mechanisms in viral airway infections.

Stimulation by menthol of Cl secretion via a Ca(2+)-dependent mechanism in canine airway epithelium

1. To investigate the effect of menthol on airway epithelial ion transport function, we studied the bioelectrical properties of canine cultured tracheal epithelium by Ussing's short-circuit technique in vitro. 2. Addition of menthol (10(-3) M) to the mucosal but not the submucosal solution increased the short-circuit current (Isc) from 6.2 +/- 0.9 to 14.0 +/- 2.2 microA cm-2 (P < 0.001), and this effect was accompanied by increases in transepithelial potential difference and conductance. The response was dose-dependent, with the maximal increase from the baseline value and the concentration required to produce a half-maximal effect (EC50) being 6.4 +/- 0.9 microA cm-2 (P < 0.001) and 40 microM, respectively. 3. Other cyclic alcohols, including menthone and cyclohexanol, had no effect on the electrical properties. 4. The menthol-induced increase in Isc was not altered by pretreatment of the cells with amiloride, indomethacin, or propranolol but was abolished by diphenylamine-2-carboxylate, furosemide or substitution of Cl with iodide in the medium. 5. Menthol (10(-3) M) increased cytosolic levels of free calcium ([Ca2+]i) from 98 +/- 12 to 340 +/- 49 nM (P < 0.01) in fura-2-loaded tracheal epithelium but did not affect the intracellular adenosine 3',5'-cyclic monophosphate content. 6. These results suggest that menthol stimulates Cl secretion across airway epithelium, probably through a Ca(2+)-dependent mechanism, and might thus influence mucociliary transport in the respiratory tract.

Air-interface cultures of guinea pig airway epithelial cells: effects of active sodium and chloride transport inhibitors on bioelectric properties

To systematically study airway epithelial barrier properties and active ion transport processes during challenge to environmental toxicants, in vitro models that closely resemble airway epithelium in vivo are required. Guinea pig tracheobronchial epithelial (GPTE) cells cultured in an air interface form a tight, confluent monolayer, which may be a more suitable model for the studies of the airway epithelial barrier in vivo. In the present study, bioelectric properties of such GPTE cell monolayers were characterized with the use of pharmacological agents. Treatment of the basolateral side with ouabain completely abolished the short-circuit current (SCC), while apical addition had little effect. Apical addition of amiloride abolished 75% of the SCC, while basal addition had little effect. Treatment of the basolateral side with furosemide or bumetanide reduced the SCC by 20%, while apical addition had no effect. Apical or basolateral terbutaline increased SCC threefold with identical time courses; results with furosemide suggest a preferential stimulation of Cl- secretion. In contrast to GPTE monolayers, canine tracheal epithelial monolayers, under short-circuit conditions, primarily secrete Cl-, possibly due to apparent species differences. The predominance of Na+ reabsorption suggests that GPTE monolayers cultured in an air interface may share similar transport properties to human airway epithelium.