The osmolyte xylitol reduces the salt concentration of airway surface liquid and may enhance bacterial killing.

The thin layer of airway surface liquid (ASL) contains antimicrobial substances that kill the small numbers of bacteria that are constantly being deposited in the lungs. An increase in ASL salt concentration inhibits the activity of airway antimicrobial factors and may partially explain the pathogenesis of cystic fibrosis (CF). We tested the hypothesis that an osmolyte with a low transepithelial permeability may lower the ASL salt concentration, thereby enhancing innate immunity. We found that the five-carbon sugar xylitol has a low transepithelial permeability, is poorly metabolized by several bacteria, and can lower the ASL salt concentration in both CF and non-CF airway epithelia in vitro. Furthermore, in a double-blind, randomized, crossover study, xylitol sprayed for 4 days into each nostril of normal volunteers significantly decreased the number of nasal coagulase-negative Staphylococcus compared with saline control. Xylitol may be of value in decreasing ASL salt concentration and enhancing the innate antimicrobial defense at the airway surface.

Increasing epithelial junction permeability enhances gene transfer to airway epithelia In vivo.

Gene transfer to airway epithelia is the most direct approach for treating the progressive lung disease associated with cystic fibrosis. However, the transduction efficiency is poor when viral vectors are applied to the mucosal surface. We reported previously that gene transfer via the apical surface of human airway epithelia in vitro was improved by formulating vectors with ethyleneglycol-bis-(2-aminoethyl ether)- N,N,N',N'-tetraacetic acid (EGTA) in a hypotonic buffer. First, we investigated the mechanism for this enhancement. When 100-nm fluorescent beads were applied to the apical surface in the presence of EGTA, paracellular deposition of the particles was noted. Transmission electron microscopy verified that the epithelial junction complex was disrupted under these conditions. The Ca(2+) chelators EGTA, 1,2-bis (2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), and ethylenediaminetetraacetic acid all caused a rapid, reversible drop in transepithelial resistance and facilitated gene transfer with retrovirus or adenovirus in vitro. When Ca(2+) chelators were applied to rabbit tracheal epithelia or human nasal epithelia in vivo, the transepithelial voltage decreased, and amiloride sensitivity was lost, suggesting that epithelial junctions opened. Importantly, this novel formulation enhanced both retroviral- and adenoviral-mediated gene transfer to rabbit tracheal epithelia in vivo. This technique may have applications for vector or drug delivery to airway epithelia and other polarized cells.

Absence of amiloride-sensitive sodium absorption in the airway of an infant with pseudohypoaldosteronism.

We report the measurement of transepithelial voltage across the nasal epithelium in a neonate with pseudohypoaldosteronism (PHA) type 1. A 5-day-old infant was seen with hyponatremia, hyperkalemia, and elevated plasma renin and aldosterone levels. Sweat Cl(-) concentration was also increased. Measurements of voltage showed a basal value of zero and the absence of an amiloride-sensitive voltage. However, voltage changed as expected for normal cyclic adenosine monophosphate-stimulated Cl(-) transport. These data demonstrate the absence of amiloride-sensitive Na(+) transport across airway epithelia in a neonate with PHA. The findings suggest that measurements of voltage could be of value in the diagnosis of PHA.

Sequential magnetic resonance imaging analysis of the maxillary sinuses: implications for a model of gene therapy in cystic fibrosis.

Serial maxillary sinus aminoglycoside lavage is an adjunctive technique increasingly employed in a variety of areas in cystic fibrosis (CF). It may be helpful in reducing revision rates for sinus surgery, in lowering rates of bronchial pseudomonal colonization after lung transplantation and in the evolving field of gene therapy for CF. The goal of this study was to assess the utility of the maxillary sinus as a model for gene transfer in cystic fibrosis. We performed serial maxillary sinus lavage, in accordance with published protocols, using tobramycin in a randomized series of five CF subjects. Lavage was performed for up to 10 days and sequential magnetic resonance imaging (MRI) scans were taken at zero, 10, 30, 60, 120 and 180 days. The 30 MRI scans were blindly scored by two examiners on the parameters of maxillary sinus aeration, averaged over the five time intervals, was significantly improved (p < 0.05) in the lavaged sinus. This study provides the first systematic image-based measure of efficacy of maxillary sinus aminoglycoside lavage, a major element of a number of clinical protocols used in the treatment of CF. The prolonged increase in aeration after lavage suggests that any further improvement potentially achievable after gene transfer would be difficult to detect, limiting the value of this system as a model of clinical efficacy of gene transfer in CF.

Comparison of DNA-lipid complexes and DNA alone for gene transfer to cystic fibrosis airway epithelia in vivo.

Cationic lipids show promise as vectors for transfer of CFTR cDNA to airway epithelia of patients with cystic fibrosis (CF). However, previous studies have not compared the effect of DNA-lipid to DNA alone. Recently, we developed a formulation of plasmid encoding CFTR (pCF1-CFTR) and cationic lipid (GL-67:DOPE) that generated greater gene transfer in mouse lung than previously described DNA-lipid vectors. Therefore, we tested the hypothesis that DNA-lipid complexes were more effective than DNA alone at transferring CFTR cDNA to airway epithelia in vivo. We administered complexes of DNA-lipid to one nostril and DNA alone to the other nostril in a randomized, double-blind study. Electrophysiologic measurements showed that DNA-lipid complexes partially corrected the Cl- transport defect. Importantly, the pCF1-CFTR plasmid alone was at least as effective as complexes of DNA with lipid. Measurements of vector-specific CFTR transcripts also showed gene transfer with both DNA-lipid and DNA alone. These results indicate that nonviral vectors can transfer CFTR cDNA to airway epithelia and at least partially restore the Cl- transport defect characteristic of CF. However, improvements in the overall efficacy of gene transfer are required to develop a treatment for CF.

Meal-induced secretion of gastrointestinal regulatory peptides is not affected by sleep.

UNLABELLED: The mechanisms responsible for the disruption of the migrating motor complex (MMC) by feeding are not fully understood. Sleep reduces the duration of the postprandial or fed pattern of motility in the intestine. This study was set out to determine if this effect is associated with sleep-induced changes in the secretion of regulatory peptides in response to food. METHODS: Duodenojejunal motility was studied in 15 healthy ambulant subjects for 2 consecutive days. On one day identical solid meals were consumed in the morning and late in the evening, the latter followed by sleep. On the other day, identical liquid meals were infused into the stomach and the duodenum in the morning and late in the evening, the latter after the onset of sleep. Plasma concentrations of gastrin, neurotensin, peptide YY (PYY), pancreatic polypeptide (PP), motilin and glucose were monitored before and after meals. Sleep significantly shortened the duration of the fed pattern after the solid meal and even more so after the liquid meal. The plasma concentrations of all peptides, except motilin, increased significantly following each meal. Blood glucose levels rose after each meal, the changes being similar with all meals. Food-induced gastrointestinal regulatory peptides secretion and intestinal absorption of glucose are not affected by sleep. The vagal response to a meal, as indicated by PP release, is intact during sleep. The results support the importance of neural mechanisms in the modulation of the postprandial pattern of intestinal motility.

Utility of the nasal model in gene transfer studies in cystic fibrosis.

Despite advances in the treatment for cystic fibrosis (CF), life expectancy for affected patients remains dramatically curtailed. Recent years have produced a spectacular increase in our understanding of the genetic, molecular and physiological bases of this disease. Gene transfer is a new and conceptually-attractive potential treatment for CF. A number of centres have undertaken preliminary human gene-therapy trials. Central to these trials has been the use of the nasal model in gene transfer studies. While the eventual target of gene therapy in CF will be the lungs, the nasal administration of vector offers a number of advantages over the tracheobronchial tree in early experimentation. Implicit in the use of the nasal model is the potential for rhinologic variables to influence the results. We review our own gene transfer studies as well as series from other institutions, considering the role of nasal factors in the experiments' outcomes. Rhinologic variables may, at least partially, potentially explain the sometimes disparate results reported in this emerging area of scientific interest.

Repeat administration of an adenovirus vector encoding cystic fibrosis transmembrane conductance regulator to the nasal epithelium of patients with cystic fibrosis.

Cystic fibrosis (CF) is a common autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator gene. Recombinant adenoviruses have shown promise as vectors for transfer of CF transmembrane conductance regulator cDNA to airway epithelia and correction of the Cl- transport defect. However, because adenovirus-mediated gene transfer is transient, use of adenovirus as a vector for treatment of CF would require repeated administration. Therefore, we evaluated repeat administration of an adenovirus vector to the nasal epithelium of patients with CF with five escalating doses of up to 10(10) infectious units. There were no detectable adverse affects. All subjects were initially seropositive but developed additional humoral immune responses. The vector partially corrected the defect in airway epithelial Cl- transport in some subjects, although there was variability between subjects and there was less correction with subsequent administration, perhaps because the immune response limited gene transfer. Future work must focus on vectors with increased efficiency and with the ability to evade host defenses.

Effects of cisapride on salivary production in normal subjects.

Cisapride improves reflux esophagitis and enhances esophageal acid clearance. To test the effect of cisapride an salivary production, we enrolled 14 healthy volunteers in a double-blind, randomized, placebo-controlled study. Subjects received cisapride, 10mg per os four times a day, or placebo for three days. Saliva, collected during fasted and fed states, was analyzed for volume and buffer capacity. Buffer capacity was expressed as the volume of 0.01 N HCl needed to titrate 1 ml of saliva to pH 6.1. Both volume and buffer capacity significantly increased during the fed state as compared to the fasted on both cisapride and placebo. Cisapride significantly enhanced the postprandial salivary volume and buffer capacity compared to placebo: 29.6 +/- 11.3 ml vs 22.9 +/- 9.5 ml and 1.07 +/- 0.31 vs 0.89 +/- 0.28, respectively (P< 0.0001). Cisapride's enhancement of salivary flow rate and buffer capacity in the fed state may be another mechanism by which it exerts its beneficial effect in patients with reflux esophagitis.

The effects of recombinant human hemoglobin on esophageal motor functions in humans.

BACKGROUND & AIMS: Nitric oxide controls lower esophageal sphincter (LES) relaxation and esophageal peristalsis in opossums, but its role in the control of esophageal motility in humans is not defined. Hemoglobin inactivates NO by binding it. Recombinant human hemoglobin (rHb1.1) was used to test the hypothesis that NO mediates esophageal motor functions in humans. METHODS: rHb1.1 or human serum albumin was administered intravenously to fasting male volunteers. Esophageal manometric studies were performed before, during, and up to 6 hours after the infusion. RESULTS: rHb1.1 increased the velocities of peristaltic contractions to produce simultaneous contractions in 6 of 9 subjects. It increased the amplitude and duration of contractile waves in the esophagus. There was no consistent effect on the resting tone of the LES, but LES relaxation was inhibited. Spontaneous, simultaneous high-pressure contractions occurred in 8 of 9 subjects. Lower retrosternal chest pain during swallowing was observed in 4 subjects. CONCLUSIONS: rHb1.1 interfered with esophageal peristalsis and LES relaxation. It precipitated esophageal spasm in some subjects. These data support the hypothesis that the timing of smooth muscle esophageal peristalsis and LES relaxation are mediated by NO. They suggest that some disorders of esophageal motor function may result from defects in NO neuromuscular communication.

Misoprostol is effective treatment for patients with severe chronic constipation.

To assess the efficacy of misoprostol in the treatment of patients with severe chronic constipation, nine such patients were enrolled in a double-blind, randomized, crossover study of misoprostol (1200 micrograms/day) or placebo, that lasted three weeks. During this period each patient received the drug for one week and placebo for another with a week washout period in between. A colonic transit study, using radiopaque markers, was performed during each of the treatment weeks, while the number of stools and their total weight was recorded by each patient for the appropriate periods. Colonic transit time was significantly and consistently decreased by misoprostol compared to placebo [66 hr +/- 10.2 vs 109.4 hr +/- 8.1 (P = 0.0005)]. Misoprostol significantly increased the total stool weight per week [976.5 g +/- 288.8 vs 434.6 g +/- 190.5 (P = 0.001)] and also significantly increased the number of stools per week compared to placebo [6.5 +/- 1.3 vs 2.5 +/- 0.11 (P = 0.01)]. The incidence of abdominal pain was similar in both groups. We concluded that misoprostol, during a short trial period, proved effective in increasing the frequency and weight of bowel movements and decreasing colonic transit time in patients with severe chronic constipation. It may be used as a therapeutic measure to treat such patients.

Morphology and pathology of radiation-induced esophagitis. Double-blind study of naproxen vs placebo for prevention of radiation injury.

Radiation-induced esophagitis can cause substantial morbidity. Experiments in lab animals have shown that pretreatment with indomethacin protects the esophagus from radiation damage. We conducted a prospective, double-blind, randomized trial of naproxen vs placebo in patients undergoing thoracic radiation therapy for lung cancer. Twenty-eight patients were enrolled, of which 26 completed the study. Sixteen patients were given a short course of radiation (30 Gy/10 fractions/2 weeks), and 10 patients were given a longer course and a larger dose (40-50 Gy/25 fractions/5 weeks). Half of the irradiated patients were treated with naproxen, 375 mg, taken orally twice a day, and half were given an identical placebo. All patients were given ranitidine 300 mg, taken orally once a day. Study drugs were taken throughout the course of radiation. Endoscopy with esophageal biopsies and brushings was performed before and on the last day of treatment. Patients kept a daily diary for symptom scoring. Symptoms such as chest pain, dysphagia, odynophagia, and/or heartburn were reported in 15 patients from both subgroups, resulting in diet restriction to liquids only in eight patients and requiring temporary discontinuation of radiation therapy in one of them. Approximately half the patients in each subgroup developed esophagitis, usually mild and usually limited to the proximal esophagus. Severity of symptoms was not proportional to the severity of esophagitis. Candidiasis was documented in eight patients, but only four had symptoms that were severe in one. We conclude that acute radiation injury to the esophagus is observed in approximately half the patients receiving radiation therapy and can result in substantial morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of graded exercise on esophageal motility and gastroesophageal reflux in nontrained subjects.

The effects of graded exercise on esophageal motility and gastroesophageal reflux were evaluated in nine nontrained subjects, using a catheter with three strain-gauge transducers connected to a solid-state datalogger and an ambulatory intraesophageal pH monitor. Subjects exercised on a stationary bike at 45%, 60%, 75%, and 90% of peak O2 uptake (VO2 max). Durations of exercise sessions and rest periods varied among subjects. Studies were performed after an overnight fast and subjects received only intravenous infusion of 5% glucose solution during the study. Plasma concentrations of gastrin, motilin, glucagon, pancreatic polypeptide (PP), and vasoactive intestinal peptide (VIP) were determined at rest and before and after each exercise session. The duration, amplitude, and frequency of esophageal contractions declined with increasing exercise intensity, and the differences were significant (P < or = 0.05) for all three variables at 90% VO2 max. The number of gastroesophageal reflux episodes and the duration of esophageal acid exposure were significantly (P < or = 0.05) increased during exercise at 90% VO2 max. Plasma regulatory peptide concentrations showed no significant changes between rest and the various exercise sessions. Thus, exercise has profound effects on esophageal contractions and gastroesophageal reflux, which are intensity dependent. These effects were not mediated by the hormones measured. The results were similar to those observed in highly trained athletes, suggesting that the effects of exercise on esophageal function are similar in trained and nontrained subjects performing at similar percentages of VO2 max, even though the absolute levels of exercise achieved in each group are different.

Effect of misoprostol on postprandial intestinal motility and orocecal transit time in humans.

We measured the effect of misoprostol (M), a PGE1 analog, on duodenojejunal postprandial motor activity and orocecal transit in eight healthy volunteers. Intestinal motility was studied by an intraluminal catheter with three strain gauge transducers connected to a solid-state datalogger, and transit time was measured by a hydrogen breath test. Subjects were studied for two consecutive days and fed twice a day with a similar, 600-kcal meal. Misoprostol (M) at 800, 400, or 200 micrograms or placebo were taken orally before every one of the four meals. Transit time was measured after the morning meal on both days, after ingestion of either 800 micrograms of M or placebo. On four occasions, following M, the normal fed pattern was not established and the migrating motor complex (MMC) was not interrupted by the meal. In all other occasions, when the higher doses of M were given, the first 1-2 hr after the meal revealed a hypoactive bowel. This effect was inconsistently seen following 200 micrograms of M. Orocecal transit time was consistently and significantly shorter after M than placebo: 48.3 +/- 9.5 min vs 104.4 +/- 4.8 min, P < 0.0001. Four subjects had diarrhea during the study. We conclude that misoprostol, particularly at higher doses, has a profound effect on intestinal postprandial motility and results in accelerated transit time. The motility changes induced by M may be responsible, in part, for its effect on transit.

Effect of graded exercise on esophageal motility and gastroesophageal reflux in trained athletes.

We evaluated the effect of graded exercise on esophageal motility and gastroesophageal reflux. We studied eight trained cyclists using a catheter with three strain-gauge transducers connected to a solid-state datalogger and an ambulatory intraesophageal pH monitor. Each study lasted 4 hr during which subjects exercised on a stationary bike for 1 hr at 60% of peak O2 uptake (O2 max), 45 min at 75% of O2 max, and for 10 min at 90% of O2 max. Subjects rested 1 hr before exercise (control period) and for 30 min between exercise sessions. Studies were performed after an overnight fast and subjects received only intravenous infusion of 5% glucose solution during the study. Plasma concentrations of gastrin, motilin, glucagon, pancreatic polypeptide (PP), and vasoactive intestinal peptide (VIP) were determined at rest and before and after each exercise session. The duration, amplitude, and frequency of esophageal contractions declined with increasing exercise intensity, and the differences were significant (P < or = 0.05) for all three variables at 90% O2 max. The number of gastroesophageal reflux episodes and the duration of esophageal acid exposure were significantly (P < or = 0.05) increased during exercise at 90% O2 max. Plasma hormone concentrations showed no significant changes between rest and the various exercise sessions. Thus, exercise has profound effects on esophageal contractions and gastroesophageal reflux which are intensity dependent. These effects are not mediated by the hormones measured.