Set-up of a pharmaceutical cell bank of Magnetospirillum gryphiswaldense MSR1 magnetotactic bacteria producing highly pure magnetosomes

We report the successful fabrication of a pharmaceutical cellular bank (PCB) containing magnetotactic bacteria (MTB), which belong to the Magnetospirillum gryphiswaldense MSR1 species. To produce such PCB, we amplified MTB in a minimal growth medium essentially devoid of other heavy metals than iron and of CMR (Carcinogenic, mutagenic and reprotoxic) products. The PCB enabled to acclimate MTB to such minimal growth conditions and then to produce highly pure magnetosomes composed of more than 99.9% of iron. The qualification of the bank as a PCB relies first on a preserved identity of the MTB compared with the original strain, second on genetic bacterial stability observed over 100 generations or under cryo-preservation for 16 months, third on a high level of purity highlighted by an absence of contaminating microorganisms in the PCB. Furthermore, the PCB was prepared under high-cell load conditions (9.108 cells/mL), allowing large-scale bacterial amplification and magnetosome production. In the future, the PCB could therefore be considered for commercial as well as research orientated applications in nanomedicine. We describe for the first-time conditions for setting-up an effective pharmaceutical cellular bank preserving over time the ability of certain specific cells, i.e. Magnetospirillum gryphiswaldense MSR1 MTB, to produce nano-minerals, i.e. magnetosomes, within a pharmaceutical setting.

A new family of structurally conserved fungal effectors displays epistatic interactions with plant resistance proteins

Recognition of a pathogen avirulence (AVR) effector protein by a cognate plant resistance (R) protein triggers a set of immune responses that render the plant resistant. Pathogens can escape this so-called Effector-Triggered Immunity (ETI) by different mechanisms including the deletion or loss-of-function mutation of the AVR gene, the incorporation of point mutations that allow recognition to be evaded while maintaining virulence function, and the acquisition of new effectors that suppress AVR recognition. The Dothideomycete Leptosphaeria maculans, causal agent of oilseed rape stem canker, is one of the few fungal pathogens where suppression of ETI by an AVR effector has been demonstrated. Indeed, AvrLm4-7 suppresses Rlm3- and Rlm9-mediated resistance triggered by AvrLm3 and AvrLm5-9, respectively. The presence of AvrLm4-7 does not impede AvrLm3 and AvrLm5-9 expression, and the three AVR proteins do not appear to physically interact. To decipher the epistatic interaction between these L. maculans AVR effectors, we determined the crystal structure of AvrLm5-9 and obtained a 3D model of AvrLm3, based on the crystal structure of Ecp11-1, a homologous AVR effector candidate from Fulvia fulva. Despite a lack of sequence similarity, AvrLm5-9 and AvrLm3 are structural analogues of AvrLm4-7 (structure previously characterized). Structure-informed sequence database searches identified a larger number of putative structural analogues among L. maculans effector candidates, including the AVR effector AvrLmS-Lep2, all produced during the early stages of oilseed rape infection, as well as among effector candidates from other phytopathogenic fungi. These structural analogues are named LARS (for Leptosphaeria AviRulence and Suppressing) effectors. Remarkably, transformants of L. maculans expressing one of these structural analogues, Ecp11-1, triggered oilseed rape immunity in several genotypes carrying Rlm3. Furthermore, this resistance could be suppressed by AvrLm4-7. These results suggest that Ecp11-1 shares a common activity with AvrLm3 within the host plant which is detected by Rlm3, or that the Ecp11-1 structure is sufficiently close to that of AvrLm3 to be recognized by Rlm3.

An efficient strategy to control fungal diseases in the field is genetic control using resistant crop cultivars. Crop resistance mainly relies on gene-for-gene relationships between plant resistance (R) genes and pathogen avirulence (AVR) genes, as defined by Flor in the 1940s. However, such gene-for-gene relationships can increase in complexity over the course of plant-pathogen co-evolution. Resistance against the plant-pathogenic fungus Leptosphaeria maculans by Brassica napus and other Brassica species relies on the recognition of effector (AVR) proteins by R proteins; however, L. maculans produces an effector that suppresses a subset of these specific resistances. Using a protein structure approach, we revealed structural analogy between several of the resistance-triggering effectors, the resistance-suppressing effector, and effectors from other plant-pathogenic species in the Dothideomycetes and Sordariomycetes classes, defining a new family of effectors called LARS. Notably, cross-species expression of one LARS effector from Fulvia fulva, a pathogen of tomato, in L. maculans resulted in recognition by resistant cultivars of oilseed rape. These results highlight the need to integrate knowledge on effector structures to improve resistance management and to develop broad-spectrum resistances for multi-pathogen control of diseases.

A new family of structurally conserved fungal effectors displays epistatic interactions with plant resistance proteins

Recognition of a pathogen avirulence (AVR) effector protein by a cognate plant resistance (R) protein triggers a set of immune responses that render the plant resistant. Pathogens can escape this so-called Effector-Triggered Immunity (ETI) by different mechanisms including the deletion or loss-of-function mutation of the AVR gene, the incorporation of point mutations that allow recognition to be evaded while maintaining virulence function, and the acquisition of new effectors that suppress AVR recognition. The Dothideomycete Leptosphaeria maculans, causal agent of oilseed rape stem canker, is one of the few fungal pathogens where suppression of ETI by an AVR effector has been demonstrated. Indeed, AvrLm4-7 suppresses Rlm3- and Rlm9-mediated resistance triggered by AvrLm3 and AvrLm5-9, respectively. The presence of AvrLm4-7 does not impede AvrLm3 and AvrLm5-9 expression, and the three AVR proteins do not appear to physically interact. To decipher the epistatic interaction between these L. maculans AVR effectors, we determined the crystal structure of AvrLm5-9 and obtained a 3D model of AvrLm3, based on the crystal structure of Ecp11-1, a homologous AVR effector candidate from Fulvia fulva. Despite a lack of sequence similarity, AvrLm5-9 and AvrLm3 are structural analogues of AvrLm4-7 (structure previously characterized). Structure-informed sequence database searches identified a larger number of putative structural analogues among L. maculans effector candidates, including the AVR effector AvrLmS-Lep2, all produced during the early stages of oilseed rape infection, as well as among effector candidates from other phytopathogenic fungi. These structural analogues are named LARS (for Leptosphaeria AviRulence and Suppressing) effectors. Remarkably, transformants of L. maculans expressing one of these structural analogues, Ecp11-1, triggered oilseed rape immunity in several genotypes carrying Rlm3. Furthermore, this resistance could be suppressed by AvrLm4-7. These results suggest that Ecp11-1 shares a common activity with AvrLm3 within the host plant which is detected by Rlm3, or that the Ecp11-1 structure is sufficiently close to that of AvrLm3 to be recognized by Rlm3.

A Method for Producing Highly Pure Magnetosomes in Large Quantity for Medical Applications Using Magnetospirillum gryphiswaldense MSR-1 Magnetotactic Bacteria Amplified in Minimal Growth Media

We report the synthesis in large quantity of highly pure magnetosomes for medical applications. For that, magnetosomes are produced by MSR-1 Magnetospirillum gryphiswaldense magnetotactic bacteria using minimal growth media devoid of uncharacterized and toxic products prohibited by pharmaceutical regulation, i.e., yeast extract, heavy metals different from iron, and carcinogenic, mutagenic and reprotoxic agents. This method follows two steps, during which bacteria are first pre-amplified without producing magnetosomes and are then fed with an iron source to synthesize magnetosomes, yielding, after 50 h of growth, an equivalent OD₅₆₅ of ~8 and 10 mg of magnetosomes in iron per liter of growth media. Compared with magnetosomes produced in non-minimal growth media, those particles have lower concentrations in metals other than iron. Very significant reduction or disappearance in magnetosome composition of zinc, manganese, barium, and aluminum are observed. This new synthesis method paves the way towards the production of magnetosomes for medical applications.

Crystal structure of the effector AvrLm4-7 of Leptosphaeria maculans reveals insights into its translocation into plant cells and recognition by resistance proteins

The avirulence gene AvrLm4-7 of Leptosphaeria maculans, the causal agent of stem canker in Brassica napus (oilseed rape), confers a dual specificity of recognition by two resistance genes (Rlm4 and Rlm7) and is strongly involved in fungal fitness. In order to elucidate the biological function of AvrLm4-7 and understand the specificity of recognition by Rlm4 and Rlm7, the AvrLm4-7 protein was produced in Pichia pastoris and its crystal structure was determined. It revealed the presence of four disulfide bridges, but no close structural analogs could be identified. A short stretch of amino acids in the C terminus of the protein, (R/N)(Y/F)(R/S)E(F/W), was well-conserved among AvrLm4-7 homologs. Loss of recognition of AvrLm4-7 by Rlm4 is caused by the mutation of a single glycine to an arginine residue located in a loop of the protein. Loss of recognition by Rlm7 is governed by more complex mutational patterns, including gene loss or drastic modifications of the protein structure. Three point mutations altered residues in the well-conserved C-terminal motif or close to the glycine involved in Rlm4-mediated recognition, resulting in the loss of Rlm7-mediated recognition. Transient expression in Nicotiana benthamiana (tobacco) and particle bombardment experiments on leaves from oilseed rape suggested that AvrLm4-7 interacts with its cognate R proteins inside the plant cell, and can be translocated into plant cells in the absence of the pathogen. Translocation of AvrLm4-7 into oilseed rape leaves is likely to require the (R/N)(Y/F)(R/S)E(F/W) motif as well as an RAWG motif located in a nearby loop that together form a positively charged region.

Effect of baclofen on the acid pocket at the gastroesophageal junction

Previous studies established that a pocket of highly acidic gastric juice is present postprandially at the gastroesophageal junction in man. The GABA-B agonist baclofen inhibits postprandial reflux events through its effects on the lower esophageal sphincter (LES). The aim of the current study was to investigate whether baclofen would affect the location and the extent of the postprandial acid pocket in healthy volunteers. Twelve healthy volunteers underwent acid pocket studies on two different occasions, at least 1 week apart. LES position was determined preprandially with pull-through manometry. Dual pH electrode and manometry probe stepwise pull-through (1 cm/minute, LES-10 to +5 cm) was performed at 30-minute intervals for 150 minutes, with administration of placebo or baclofen 40 mg after the first and ingestion of a liquid meal after the second pull-through. After placebo, a significant drop in intragastric gastric pH was present at the gastroesophageal junction after the meal, reflecting the acid pocket, and this was associated with a drop in LES pressure. Baclofen did not affect the presence of the acid pocket, but prevented the postprandial drop in LES pressure, and the extent of the acid pocket above the upper margin of the manometrically located LES was significantly decreased by baclofen (1.6 ± 0.7 vs. 0.3 ± 0.4 cm at 60 minutes, 2.2 ± 0.6 vs. 0.2 ± 0.6 at 90 minutes, and 1.5 ± 0.5 vs. 0.7 ± 0.7 cm at 120 minutes, all P < 0.05). Baclofen does not alter the intragastric acid pocket, but limits its extension into the distal esophagus, probably through an increase in postprandial LES pressure.

Randomized clinical trial: effect of the 5-HT4 receptor agonist revexepride on reflux parameters in patients with persistent reflux symptoms despite PPI treatment

BACKGROUND

Approximately, 20-30% of patients with gastro-esophageal reflux disease (GERD) experience persistent symptoms despite treatment with proton pump inhibitors (PPIs). These patients may have underlying dysmotility; therefore, targeting gastric motor dysfunction in addition to acid inhibition may represent a new therapeutic avenue. The aim of this study was to assess the pharmacodynamic effect of the prokinetic agent revexepride (a 5-HT4 receptor agonist) in patients with GERD who have persistent symptoms despite treatment with a PPI.

METHODS

This was a phase II, exploratory, multicenter, randomized, placebo-controlled, double-blind, parallel-group study in patients with GERD who experienced persistent symptoms while taking a stable dose of PPIs (ClinicalTrials.gov identifier: NCT01370863). Patients were randomized to either revexepride (0.5 mg, three times daily) or matching placebo for 4 weeks. Reflux events and associated characteristics were assessed by pH/impedance monitoring and disease symptoms were assessed using electronic diaries and questionnaires.

KEY RESULTS

In total, 67 patients were enrolled in the study. There were no significant differences between study arms in the number, the mean proximal extent or the bolus clearance times of liquid-containing reflux events. Changes from baseline in the number of heartburn, regurgitation, and other symptom events were minimal for each treatment group and no clear trends were observed.

CONCLUSIONS & INFERENCES

No clear differences were seen in reflux parameters between the placebo and revexepride groups.

Structural and functional analysis of the fibronectin-binding protein FNE from Streptococcus equi spp. equi

Streptococcus equi is a horse pathogen belonging to Lancefield group C. Infection by S. equi ssp. equi causes strangles, a serious and highly contagious disease of the upper respiratory tract. S. equi ssp. equi secretes a fibronectin (Fn)-binding protein, FNE, that does not contain cell wall-anchoring motifs. FNE binds to the gelatin-binding domain (GBD) of Fn, composed of the motifs (6) FI (12) FII (789) FI . FNE lacks the canonical Fn-binding peptide repeats observed in many microbial surface components recognizing adhesive matrix molecules. We found that the interaction between FNE and the human GBD is mediated by the binding of the disordered C-terminal region (residues 208-262) of FNE to the (789) FI GBD subfragment. The crystal structure of FNE showed that it is similar to the minor pilus protein Spy0125 of Streptococcus pyogenes, found at the end of pilus polymers and responsible for adhesion. FNE and Spy0125 both have a superimposable internal thioester bond between highly conserved Cys and Gln residues. Small-angle X-ray scattering of the FNE-(789) FI complex provided a model that aligns the C-terminal peptide of FNE with the E-strands of the FI domains, adopting the β-zipper extension model observed in previous structures of microbial surface components recognizing adhesive matrix molecule adhesion peptides bound to FI domains.

Patients with esophageal motility disorders show distinct patterns based on axial force measurements

BACKGROUND

Using manometry, the classification of motility-related disorders in the esophagus is vague and overlapping. We present a new method, which combines manometry and axial force measurements in a single catheter.

AIM

The aim was to examine the manometric and axial force recordings during swallows.

METHODS

Recordings from 20 patients suffering from diffuse esophageal spasms (DES) (8), achalasia (5) and other diseases including gastro-oesophageal reflux (7) were compared to recordings made in ten healthy subjects. The probe was capable of measuring axial force 6.5-cm proximal to the lower esophageal sphincter (LES) and pressures 8-, 10- and 12-cm proximal to the LES. After insertion, five dry and five wet swallows were made. Swallows were repeated with 0, 2, 4 and 6 ml of water in a bag mounted distal to the axial force recording site. Each contraction was analysed for duration and amplitude, and was categorised according to its configuration.

RESULTS

The number of failed contractions measured with axial force was lower for the achalasia (P < 0.001) and DES groups (P < 0.001) compared to the healthy volunteers. The number of multi-peaked contractions was unchanged for the achalasia and DES groups while it increased for the group of healthy volunteers. On several occasions a negative traction force was encountered though the manometric pattern appeared normal.

CONCLUSIONS

Measurements of axial force generated by primary peristalsis provide additional information about esophageal neuromuscular function in different diseases that is not demonstrable with manometry alone.

Effect of buspirone, a 5-HT1A receptor agonist, on esophageal motility in healthy volunteers

There are limited data concerning the effects of 5-HT(1A) receptor activation on esophageal motility. Sumatriptan, a 5-HT(1A) receptor agonist, was recently reported to enhance esophageal peristalsis after intravenous administration. Buspirone, an orally available 5-HT(1A) receptor agonist, was shown to modulate gastroduodenal motor function. Our aim was to evaluate the effect of buspirone on esophageal motility of healthy volunteers. On two separate visits, 20 healthy volunteers aged 21-29 years (nine women) underwent esophageal manometry before and 10, 30, and 60 minutes after the administration of buspirone 20-mg or placebo capsule, according to a double-blind crossover design. At each time point, we compared buspirone and placebo effects on: resting pressure of the lower esophageal sphincter (LES); residual pressure and duration of LES relaxation; amplitude, duration, and onset velocity of esophageal body contractions, during 10 swallows of 5 mL of water. Significant analysis of variance differences (P < 0.05) are presented as mean ± standard deviation. Buspirone significantly increased mean distal esophageal wave amplitude (151 vs. 87 mmHg, P < 0.05) and duration (6.1 vs. 4.2 seconds, P < 0.05). Similarly, buspirone significantly increased mean LES resting pressure (26 vs. 21 mmHg, P < 0.05) and mean residual LES pressure (7.9 vs. 2 mmHg, P < 0.05), whereas reduced mean LES relaxation duration (7.2 vs. 8.0 seconds, P < 0.05) and mean distal onset velocity (7.6 vs. 14.7 cm/second, P < 0.05). Buspirone enhances esophageal peristalsis and LES function in healthy volunteers. Further study is warranted on the effects of buspirone on esophageal function and symptoms in patients with ineffective esophageal motility.

A double-blind sham-controlled study of the effect of radiofrequency energy on symptoms and distensibility of the gastro-esophageal junction in GERD

OBJECTIVES

Several studies have reported symptom relief in gastro-esophageal reflux disease (GERD) patients treated with radiofrequency delivery (Stretta procedure) at the gastro-esophageal junction (GEJ), but the mechanism underlying this improvement is unclear. The objective of this study was to test the hypothesis that Stretta alters GEJ resistance.

METHODS

We conducted a double-blind randomized cross-over study of Stretta and sham treatment. Consecutive GERD patients were included in the study. The study was conducted in a tertiary care center. Patients underwent two upper gastrointestinal endoscopies with 3 months interval, during which active or sham Stretta treatment was performed in a randomized double-blind manner. Symptom assessment, endoscopy, manometry, 24-h esophageal pH monitoring, and a distensibility test of the GEJ were done before the start of the study and after 3 months.

RESULTS

Barostat distensibility test of the GEJ before and after administration of sildenafil was the main outcome measure. In all, 22 GERD patients (17 females, mean age 47±12 years) participated in the study; 11 in each group. Initial sham treatment did not affect any of the parameters studied. Three months after initial Stretta procedure, no changes were observed in esophageal acid exposure and lower esophageal sphincter (LES) pressure. In contrast, symptom score was significantly improved and GEJ compliance was significantly decreased. Administration of sildenafil, an esophageal smooth muscle relaxant, normalized GEJ compliance again to pre-Stretta level, arguing against GEJ fibrosis as the underlying mechanism.

CONCLUSIONS

The limitation of this study was reflux evaluation did not include impedance monitoring. In this sham-controlled study, Stretta improved GERD symptoms and decreased GEJ compliance. Decreased GEJ compliance, which reflects altered LES neuromuscular function, may contribute to symptomatic benefit by decreasing refluxate volume.

Gastric emptying and different types of reflux in adult patients with cystic fibrosis

BACKGROUND

Increased gastro-oesophageal reflux (GER) is common in patients with cystic fibrosis (CF). Previous studies showed delayed gastric emptying (GE) and a high prevalence of bile acids in saliva suggesting duodenogastro-oesophageal reflux (DGER).

AIM

To assess different types of reflux (acid, weakly acidic and bile) and their relationship with rate of GE in adult CF patients.

METHODS

Gastric emptying was assessed in 33 CF patients using breath tests, reflux was monitored in 42 patients using impedance-pH-metry and 14 CF patients underwent combined impedance-pH-Bilitec monitoring.

RESULTS

Delayed GE was found in 33%, increased GER (predominantly acid) in 67% and pathological DGER in 35% of the CF patients. There was a significant correlation between oesophageal bile and acid exposure (P < 0.0001, r = 0.85). Patients with increased DGER had a higher proximal extent of reflux compared to those without DGER [17 (9-35) vs. 5 (1-12), P = 0.04]. There was no correlation between GE and reflux parameters, however, in a subgroup of 10 patients studied by impedance-pH-Bilitec and GE, there was a strong correlation between GE rate and bile exposure (P = 0.005, r = 0.83).

CONCLUSIONS

Delayed gastric emptying is present in 1/3 of patients with cystic fibrosis. There is a subgroup of these patients with both delayed gastric emptying and increased acidic duodenogastro-oesophageal reflux with high proximal extent and risk of aspiration. Controlled studies should be performed to evaluate the effect of prokinetics or antireflux surgery on the clinical cystic fibrosis evolution in these patients.

Increasing body weight enhances prevalence and proximal extent of reflux in GERD patients 'on' and 'off' PPI therapy

BACKGROUND

Increased body weight is associated with higher intragastric pressure. Proximal extent of reflux is a determinant of symptoms in patients with gastro-esophageal reflux disease (GERD). We aimed to investigate the association between body mass index (BMI) and abdominal circumference on the incidence and proximal extent of reflux.

METHODS

A total of 95 patients [37 men, age 51(16-82) years] with typical and/or atypical GERD symptoms underwent 24 h impedance-pH monitoring. Forty-nine patients were studied 'off' and 46 'on' proton pump inhibitors (PPI) treatment. Reflux was classified as acid (pH < 4) or weakly acidic (pH 4-7). Proximal extent was defined as the number of reflux events reaching ≥15 cm above the lower esophageal sphincter. Body mass index and abdominal circumference (cm) were assessed.

KEY RESULTS

In patients 'off' PPI, there was a correlation between BMI and esophageal acid exposure (ρ = 0.53, P < 0.001), volume exposure (ρ = 0.48, P < 0.001), total number of reflux events (ρ = 0.47, P < 0.001) and number of acid reflux events (ρ = 0.49, P < 0.001). In patients 'on' PPI there was a correlation between BMI and esophageal acid exposure (ρ = 0.32, P = 0.03), volume exposure (ρ = 0.46, P < 0.01) and total number of reflux events (ρ = 0.33, P = 0.03). Similar correlations were found between abdominal circumference and reflux. A correlation between BMI and proximal extent of reflux was present in patients 'off' PPI (ρ = 0.32, P = 0.03). In patients 'on' PPI, we found a correlation between abdominal circumference and proximal extent (ρ = 0.31, P = 0.03).

CONCLUSIONS & INFERENCES

Body mass index and abdominal circumference may contribute to GER and its proximal extent, in patients 'on and 'off' PPI. Further studies investigating the role of weight reduction in the control of GERD symptoms are warranted.

Modulation of the postprandial acid and bile pockets at the gastro-oesophageal junction by drugs that affect gastric motility

BACKGROUND

Previous studies have established the presence of a postprandial acid pocket at the gastro-oesophageal junction.

AIMS

To investigate whether altering gastric motility would affect the location and the extent of postprandial acid pockets in healthy volunteers and also to study the presence of bile in this pocket.

METHODS

A total of 16 healthy volunteers underwent pH and Bilitec probe stepwise pull-through to measure regional differences in pH and bile absorbance before and 10, 30 and 50 min after a liquid meal. At the start of the meal, saline, erythromycin or sumatriptan was administered.

RESULTS

After saline, ingestion of a meal induced an acid pocket, with a mean pH drop of 2.26 (compared to 0.25 before the meal, P < 0.05) and a nadir pH of 2.71. The acid pocket persisted 30 and 50 min postprandially (pH drops 1.59 and 1.68 and nadir pH 3.17 and 2.52 respectively). Compared with saline, erythromycin significantly suppressed the pH drop and nadir pH (on average 0.66 and 3.4 at 10 min; comparable patterns at 30 and 50 min). After sumatriptan a significantly lower nadir pH was observed at 30 and 50 min (respectively 2.02 and 1.74, P < 0.05 compared with saline). A postprandial bile pocket was noted in 50% of pull-throughs after saline, compared to 78% after erythromycin and 31% after sumatriptan.

CONCLUSIONS

The presence of a bile pocket in a subset of the subjects confirms the heterogeneity of postprandial intragastric contents. Erythromycin disrupts the acid pocket but increases the presence of bile, while sumatriptan has opposite effects.

Review article: the pathophysiology, differential diagnosis and management of rumination syndrome

BACKGROUND

Rumination syndrome, characterised by the effortless, often repetitive, regurgitation of recently ingested food into the mouth, was originally described in children and in the developmentally disabled. It is now well-recognised that rumination syndrome occurs in patients of all ages and cognitive abilities.

AIM

To review a scholarly review on our current understanding of the rumination syndrome.

METHODS

The review was conducted on the basis of a medline search to identify relevant publications pertaining to the pathophysiology, clinical diagnosis and management of rumination syndrome.

RESULTS

The Rome III consensus established diagnostic criteria for rumination syndrome in adults, children and infants. A typical history can be highly suggestive but oesophageal (high resolution) manometry/impedance with ingestion of a meal may help to distinguish rumination syndrome from other belching/regurgitation disorders. The pathophysiology is incompletely understood, but involves a rise in intra-gastric pressure, generated by a voluntary, but often unintentional, contraction of the abdominal wall musculature, at a time of low pressure in the lower oesophageal sphincter, causing retrograde movement of gastric contents into the oesophagus. To date, controlled trials in the treatment rumination syndrome are lacking. The mainstay of treatment for rumination syndrome is explanation and behavioural treatment which consists of habit reversal techniques that compete with the urge to regurgitate. Chewing gum, prokinetics, baclofen and even antireflux surgery have been proposed as adjunctive therapies, but high quality studies are generally lacking.

CONCLUSIONS

Rumination is an under-recognised condition with incompletely understood pathophysiology. Behavioural therapy seems effective, but controlled treatment trials are lacking.

Effect of rimonabant on oesophageal motor function in man

BACKGROUND

Cannabinoid type 1 (CB1) receptors are implicated in the control of transient lower oesophageal sphincter relaxations (TLESRs) in animals. In man, it is unclear whether CB1 receptors are involved in the control of oesophageal function.

AIM

To study the effects of the CB1 receptor antagonist rimonabant on fasting and postprandial LES function in healthy subjects.

METHODS

Twelve healthy volunteers underwent two oesophageal manometry studies with administration of wet swallows and a meal after 3 days' premedication with placebo or rimonabant 20 mg.

RESULTS

Rimonabant did not significantly alter preprandial LES pressure (21.1±4.0 vs. 17.3±3.0 mmHg, N.S.), but postprandial LES pressures were significantly enhanced (9.9±1.9 vs.17.1±2.7 mmHg in the first and 10.0±1.4 vs. 19.3±3.6 mmHg in the second postprandial hour, both P<0.05). Swallow-induced relaxations and amplitude of peristaltic contractions were not altered, but rimonabant significantly increased the duration of peristaltic contractions at all time points (e.g. 5.0±0.3 vs. 8.0±0.3s preprandially and 5.0±0.2 vs. 8.2±0.3s at 60 min postprandially, both P<0.01). The number of postprandial TLESRs (3.1±0.5 vs. 1.2±0.5, P<0.05) and acid reflux episodes (1.4±0.2 vs. 0.3±0.1, P<0.05) were significantly lower after rimonabant.

CONCLUSION

The CB1 receptor antagonist rimonabant enhances postprandial LES pressure and decreases TLESRs in healthy subjects.

The relationship between gastroesophageal reflux and cough in children with chronic unexplained cough using combined impedance-pH-manometry recordings

INTRODUCTION

Assessment of the reflux-cough association in children is challenging. Esophageal (impedance) pH recording is sensitive to recognize reflux. However, cough recorded by an event marker, possibly lacks accuracy. We aimed to study the exact time relationship between reflux and cough in children with chronic cough.

METHODS

Twenty-six children (12 boys; 1-10.5 years) with chronic unexplained cough underwent ambulatory impedance-pH-manometry recordings. Manometry was used for precise cough recognition. Reflux was assessed with impedance-pH monitoring and defined as acid (pH <4), weakly acidic (WA) (pH 4-7), weakly alkaline (WALK) (pH ≥7), or acid only (pH <4 for ≥4 sec without impedance pattern). Cough was considered "induced by" reflux, if it started ≤2 min after reflux. The Symptom Association Probability (SAP) was calculated and considered positive if >95%. Cough-induced reflux if it occurred 30 sec before the reflux event.

RESULTS

Impedance-pH detected 30 (21-52) reflux episodes/patient (55.2% acid, 41.5% WA, and 3.3% WALK). Additionally 59 acid only events were identified [1 (0-21)/patient]. Manometry detected 47 (5-203) cough bursts/patient. Reflux-cough was found in 22/26 patients. Ten patients had a +SAP for reflux-cough (one acid, six WA, and three acid + WA gastroesophageal reflux [GER]), of which nine had a normal acid exposure. Six out of 10 patients with +SAP using manometry had a +SAP using the event marker. Cough-reflux was detected in 19 patients [3 (0-7)/patient]. Only a small fraction of the esophageal acid exposure [9.6 (0.4-31.8%)] was secondary to cough.

CONCLUSION

Both acid and WA GER may precede cough in children with unexplained cough, but cough does not induce GER. Objective cough recording improves symptom association analysis.

Bile acids aspiration reduces survival in lung transplant recipients with BOS despite azithromycin

Azithromycin (AZM) improved bronchiolitis obliterans syndrome (BOS) and reduced aspiration in lung transplant (LTx) recipients. We hypothesize that AZM could improve graft and overall survival more efficiently in LTx patients with BOS who have bile acid (BA) aspiration by protecting against the aspiration-induced progression of BOS. The goal was to compare FEV(1) (% baseline), BOS progression and overall survival in LTx recipients treated with AZM for BOS, both with versus without BA aspiration. Therefore, LTx recipients treated with AZM for BOS were recruited and broncho-alveolar lavage (BAL) samples were analyzed for the presence of BA and neutrophilia before the start of AZM treatment. Short-term effect of AZM on FEV(1) and BAL neutrophilia was assessed, progression of BOS and survival were followed-up for 3 years and results were compared between patients with/without BA aspiration. 19/37 LTx patients had BA in BAL. BA aspiration predisposed to a significantly worse outcome, in terms of decline in FEV(1) , progression of BOS ≥ 1 and survival. AZM does not seem to protect against the long-term allograft dysfunction caused by gastroesophageal reflux (GER) and aspiration and an additional treatment targeting aspiration may be indicated in those LTx patients.

The effects of itopride on oesophageal motility and lower oesophageal sphincter function in man

BACKGROUND

Itopride is a new prokinetic agent that combines antidopaminergic and cholinesterase inhibitory actions. Previous studies suggested that itopride improves heartburn in functional dyspepsia, and decreases oesophageal acid exposure in gastro-oesophageal reflux disease. It remains unclear whether this effect is due to effects of itopride on the lower oesophageal sphincter (LES).

AIMS

To study the effects of itopride on fasting and postprandial LES function in healthy subjects.

METHODS

Twelve healthy volunteers (five men; 32.6 ± 2.0 years) underwent three oesophageal sleeve manometry studies after 3 days premedication with itopride 50 mg, itopride 100 mg or placebo t.d.s. Drug was administered after 30 min and a standardized meal was administered after 90 min, with measurements continuing to 120 min postprandially. Throughout the study, 10 wet swallows were administered at 30-min intervals, and gastrointestinal symptoms were scored on 100 mm visual analogue scales at 15-min intervals.

RESULTS

Lower oesophageal sphincter resting pressures, swallow-induced relaxations and the amplitude or duration of peristaltic contractions were not altered by both doses of itopride, at all time points. Itopride pre-treatment inhibited the meal-induced rise of transient LES relaxations (TLESRs).

CONCLUSIONS

Itopride inhibits TLESRs without significantly affecting oesophageal peristaltic function or LES pressure. These observations support further studies with itopride in gastro-oesophageal reflux disease.

Treatment of gastro-esophageal reflux disease: the new kids to block

Refractory gastro-esophageal reflux disease (GERD), defined as persistent symptoms despite proton pump inhibitor (PPI) therapy, is an increasingly prevalent condition and is becoming a major challenge for the clinician. Since non-acidic reflux may be associated with symptoms persisting during PPI treatment, the lower esophageal sphincter (LES), the most important barrier protecting against reflux, has become an important target for the treatment of (refractory) GERD. Preclinical research has identified several receptors that are involved in the control of transient lower esophageal sphincter relaxations (TLESRs), the predominant mechanism of both acid and non-acidic reflux events, and several drugs have now been tested in humans. The GABA(B) agonist baclofen has demonstrated to effectively reduce the rate of TLESRs and the amount of reflux in both GERD patients and healthy volunteers. Nevertheless, the occurrence of central side effects limits its clinical use for the treatment of GERD. Several analogues are being developed to overcome this limitation and have shown promising results. Additionally, metabotropic glutamate receptor 5 (mGluR5) receptor antagonists have shown to reduce both acid and non-acidic reflux in GERD patients and several molecules are currently being evaluated. Although CB(1) antagonists have been shown to reduce TLESRs, they are also associated with central side effects, limiting their clinical applicability. Despite the identification of several potentially interesting drugs, the main challenge for the future remains the reduction of central side effects. Moreover, future studies will need to demonstrate the efficacy of these treatments in patients with refractory GERD.

Influence of intra-oesophageal capsaicin instillation on heartburn induction and oesophageal sensitivity in man

Heartburn is the most typical gastro-oesophageal reflux disease (GERD) symptom. The transient receptor potential vanilloid receptor-1 (TRPV(1)) is a candidate mediator of heartburn. Exposure of TRPV(1) to capsaicin is characterized by activation, followed by desensitization. Our aim was to investigate the effect of intra-oesophageal capsaicin instillation on oesophageal symptom perception (activation) and on sensitivity to oesophageal acid perfusion and oesophageal balloon distention (desensitization). In a first protocol (n = 10), saline or capsaicin solution were instilled in the mid-oesophagus and symptoms were rated at 5-min intervals for 60 min. In a second study (n = 10), oesophageal 0.1 N hydrochloric acid perfusion was performed 60 min after pretreatment with saline, low or high dose capsaicin. In a third study (n = 10), sensitivity to oesophageal balloon distention was determined before and at 30-min intervals up to 90 min after pretreatment with saline, low or high dose capsaicin. Areas under the curve (AUC) for symptom intensities under different conditions were calculated and compared with Kruskal-Wallis test. Oesophageal capsaicin instillation induced transient symptoms of retrosternal and epigastric burning in a dose-dependent fashion. After oesophageal capsaicin or saline instillation, there was no difference in symptom pattern and intensities induced by oesophageal acid perfusion. After oesophageal capsaicin or saline instillation, sensitivity to oesophageal balloon distention and oesophageal compliance were not significantly altered. Oesophageal instillation of the TRPV(1) receptor agonist capsaicin induces symptoms of retrosternal and epigastric burning in a dose-dependent fashion. Pretreatment with capsaicin does not desensitize the oesophagus to acid perfusion or to balloon distention.

The spectrum of motor function abnormalities in gastroesophageal reflux disease and Barrett's esophagus

Barrett's esophagus has traditionally been regarded as the most severe end of the spectrum of gastroesophageal reflux disease and is of great clinical importance in view of the association with esophageal adenocarcinoma. Studies have documented high levels of esophageal acid exposure in Barrett's esophagus. Various pathogenetic mechanisms underlie this phenomenon. These include abnormalities in esophageal peristalsis, defective lower esophageal sphincter pressures, gastric dysmotility and bile reflux. Whilst these factors provide evidence for an acquired cause of Barrett's esophagus, an underlying genetic predisposition cannot be ruled out. Although the past decade has brought about many new discoveries in the pathogenesis of Barrett's esophagus, it has also added further controversy to this complex disorder. A detailed analysis of the gastrointestinal motor abnormalities occurring in Barrett's esophagus follows, with a review of the currently available literature and an update on this condition that continues to be of interest to the gastroenterologist.

Azithromycin reduces gastroesophageal reflux and aspiration in lung transplant recipients

Azithromycin (AZI) is a macrolide antibiotic that improves lung function in lung transplant recipients (LTx). Gastroesophageal reflux (GER) has been implicated in the pathogenesis of chronic rejection after LTx. Macrolide antibiotics may affect GER by modifying esophageal and gastric motility. The purpose of this study was to evaluate the effect of AZI on GER and gastric aspiration after LTx. Acid and weakly acidic GER was measured with 24-h pH-impedance monitoring in 47 LTx patients (12 patients "on" AZI). Gastric aspiration was assessed in a separate group of 30 LTx patients before and after AZI by measurements of pepsin and bile acid in bronchoalveolar lavage fluid (BALF). Patients "on" AZI had a significant lower total number of reflux events [41 (30-61) vs. 22.5 (7-37.5)], number of acid reflux events [24 (16-41) vs. 8 (4-18)], esophageal acid exposure [2.9% (0.7-7.3) vs. 0.2% (0.1-2.0)], bolus exposure [0.73% (0.5-1.4) vs. 0.21% (0.12-0.92)], and proximal extent of reflux [14 (9-24) vs. 5 (2-7)]. AZI reduced the concentration of bile acids in BALF without affecting levels of pepsin. LTx patients "on" AZI have less GER and bile acids aspiration. This effect might be due to enhanced esophageal motility and accelerated gastric emptying.

Regional oesophageal sensitivity to acid and weakly acidic reflux in patients with non-erosive reflux disease

The mechanisms underlying symptoms in non-erosive reflux disease (NERD) remain to be elucidated. Non-erosive reflux disease patients appear to be more sensitive to intraluminal stimula than erosive patients, the proximal oesophagus being the most sensitive. In order to assess regional oesophageal changes in reflux acidity and sensitivity to reflux, according either to the acidity or the composition of the refluxate, combined multiple pH and multiple pH-impedance (pH-MII) was performed in 16 NERD patients. According to multiple pH-metry, 29% and 12% of reflux events reached the middle and proximal oesophagus respectively, and 35% and 19% according to conventional pH-MII (P < 0.05). The per-individual analysis confirmed the difference between the two techniques. According to combined distal and proximal pH-MII, approximately 30% of distal acid reflux became weakly acidic at the proximal oesophagus. In all patients, the frequency of symptomatic refluxes, both acid and weakly acidic, was significantly higher at the proximal, compared with distal oesophagus (25 +/- 8%vs 11 +/- 2% for acid reflux and 27 +/- 8%vs 8 +/- 2% for weakly acidic reflux; P < 0.05). Compared with multiple pH-metry, pH-MII shows a higher sensitivity in the detection of proximal reflux. As approximately 30% of acid reflux becomes weakly acidic along the oesophageal body, to better characterize proximal reflux, in clinical practice, combined proximal pH-impedance monitoring should be used. In NERD patients, the proximal oesophagus seems to be more sensitive to both acid and weakly acidic reflux.

Continuous distal oesophageal acidification decreases postprandial gastric acidity in healthy human subjects

BACKGROUND

Previously, we hypothesized that exposing the distal oesophagus to acid signals the stomach to decrease gastric acidity.

AIM

To test the hypothesis that exposing the distal oesophagus to acid signals the stomach to decrease gastric acidity.

METHODS

Twenty-two healthy humans ingested a standard meal containing [(14)C]octanoic acid and [(13)C]glycine over 30 min on 2 separate occasions. Gastric pH was measured for 90 min before and 240 min after the meal. 10 mm HCl was infused continuously at 1 mL/min into either the distal oesophagus or stomach in a 2-way crossover fashion for 60 min before and 240 min after the meal. Gastric emptying of solid and liquid were determined with breath tests.

RESULTS

Compared to gastric infusion, oesophageal infusion significantly decreased gastric acidity after the meal, but not before the meal and the magnitude of the decrease varied directly with gastric acidity. Gastric emptying of solid or liquid with oesophageal infusion was not significantly different from that with gastric infusion.

CONCLUSIONS

These findings support the hypothesis of the existence of a physiological oesophago-gastric feedback mechanism that might contribute to regulation of postprandial gastric acidity. Oesophageal acidification might decode gastric information and signal the stomach to decrease gastric acidity. Further studies are needed to assess the characteristics of such feedback mechanism in-patients with gastro-oesophageal reflux disease (GERD).

Short exposure of oesophageal mucosa to bile acids, both in acidic and weakly acidic conditions, can impair mucosal integrity and provoke dilated intercellular spaces

BACKGROUND

Severe duodeno-gastro-oesophageal reflux (DGOR) is a risk factor for oesophagitis and Barrett's oesophagus. Patients with non-erosive reflux disease (NERD) have a slight increase in DGOR. Patients with gastro-oesophageal reflux disease (GORD), who are taking proton pump inhibitors (PPIs), still have reflux but of weakly acidic pH and persistence of bile. In these two groups of patients, heartburn might be due to increased oesophageal mucosal permeability and dilated intercellular spaces (DIS). We aimed to assess whether experimental short exposure of the oesophageal mucosa to bile acids, in low concentrations (at acidic, weakly acidic and neutral conditions) can increase mucosal permeability and provoke DIS.

METHODS

Rabbit oesophageal mucosa was studied in diffusion and Ussing chambers. We assessed the effects of different solutions containing bile acids, applied to the mucosal side, on transepithelial electrical resistance (R(T)) and permeability to fluorescein. The diameter of intercellular spaces was assessed by using transmission electron microscopy.

RESULTS

Incubation of oesophageal mucosa with acidic solutions (pH 2.0) containing a range of bile acids (0.5-5 mmol/l) markedly decreased R(T) and increased mucosal permeability. Weakly acidic solutions (pH 5.0), and to some extent neutral solutions (pH 7.4), containing some bile acids also decreased R(T) and increased permeability, although the effects were much less marked and in some combinations no effect was seen. Exposure to bile acids provoked DIS in acid and weakly acidic conditions but not in neutral (pH 7.4) solutions.

CONCLUSIONS

Experimental short exposure of the oesophageal mucosa to solutions with a bile acid concentration and acidity similar to that observed in the gastric contents of patients with NERD or ERD, and who are taking PPIs, may impair oesophageal mucosal integrity and even induce dilated intercellular spaces. Such a situation could, theoretically, underlie the occurrence and/or persistence of symptoms in these patients.

Nutcracker oesophagus: association with chest pain and dysphagia controlling for gastro-oesophageal reflux

BACKGROUND

The association between nutcracker oesophagus, gastro-oesophageal reflux and their symptoms is controversial.

AIM

To evaluate the association of nutcracker oesophagus with chest pain and dysphagia controlling for gastro-oesophageal reflux.

METHODS

From a database of 935 consecutive patients investigated with oesophageal manometry and pH-metry, we selected all patients with nutcracker oesophagus including diffuse and segmental patterns. Patients with normal oesophageal peristalsis served as controls. Symptoms assessment, manometry testing and 24h oesophageal pH monitoring off acid-suppressive medications were performed following a standardized protocol. The associations between nutcracker oesophagus and symptoms were assessed by logistic regression analysis.

RESULTS

Nutcracker oesophagus was found in 60 patients (6.4%), of which 30 had diffuse nutcracker oesophagus and 30 had segmental nutcracker oesophagus. The control group was composed by 656 patients with normal oesophageal peristalsis. Diffuse nutcracker oesophagus was associated with chest pain (odds ratio 4.3; 95% CI 1.9-9.9; P<0.0001) and dysphagia (odds ratio 5.3; 95% CI 2.3-12.2; P<0.0001), whereas segmental nutcracker oesophagus was associated with chest pain (odds ratio 2.8; 95% CI 1.1-6.9; P=0.026), controlling for total oesophageal acid exposure, age, sex and lower oesophageal sphincter (LOS) pressure.

CONCLUSION

This study suggests that both diffuse and segmental nutcracker oesophagus should be regarded as meaningful abnormalities and not mere manometric curiosities.

Gastro-oesophageal reflux and aspiration of gastric contents in adult patients with cystic fibrosis

BACKGROUND

Gastro-oesophageal reflux (GOR) is increased in cystic fibrosis (CF), but its prevalence, characteristics, association with gastric aspiration and respiratory impact are not well characterised. We investigated acid and weakly acidic reflux, aspiration and respiratory symptoms/function in adult CF patients.

METHODS

Thirty-three CF patients [19 men; 29 (18-55) years, [10 post-lung transplant (LTx)] underwent impedance-pH monitoring for detection of acid (pH<4) and weakly acid GOR (pH 4-7). In 16 patients cough was objectively recorded with oesophageal manometry, and the symptom association probability (SAP) was calculated. Saliva and bronchoalveolar lavage fluid (BALF) were tested for bile acids.

RESULTS

Twenty-eight patients had increased GOR (21 acid, 5 weakly acidic and 2 acid+weakly acidic) and 10 had a positive SAP for reflux cough. GOR parameters were similar in non-LTx and post-LTx CF patients. The sequence reflux cough was significantly more common than cough reflux. Sixteen of 38 patients had bile acids in saliva and 6/10 in BALF and this was almost exclusively observed in patients with genotype DF508/DF508. Only 12/28 with increased GOR and 9/22 with bile acids in saliva/BALF had typical reflux symptoms. There was a positive correlation (r = 0.53, p = 0.03) between oesophageal acid exposure and cough. SAP-positive patients with for reflux cough had a lower lung function than SAP-negative patients.

CONCLUSION

Increased GOR is prevalent in CF and not secondary to cough. Acid GOR is common, but weakly acidic GOR may also occur. CF patients have a high risk of aspiration and reflux seems to be associated with more cough and poorer lung function. Outcome studies with intense anti-reflux therapy are needed to confirm the deleterious role of reflux in CF progression.

The structure of an archaeal homodimeric ligase which has RNA circularization activity

The genome of Pyrococcus abyssi contains two open reading frames encoding proteins which had been previously predicted to be DNA ligases, Pab2002 and Pab1020. We show that while the former is indeed a DNA ligase, Pab1020 had no effect on the substrate deoxyoligo-ribonucleotides tested. Instead, Pab1020 catalyzes the nucleotidylation of oligo-ribonucleotides in an ATP-dependent reaction, suggesting that it is an RNA ligase. We have solved the structure of Pab1020 in complex with the ATP analog AMPPNP by single-wavelength anomalous dispersion (SAD), elucidating a structure with high structural similarity to the catalytic domains of two RNA ligases from the bacteriophage T4. Additional carboxy-terminal domains are also present, and one of these mediates contacts with a second protomer, which is related by noncrystallographic symmetry, generating a homodimeric structure. These C-terminal domains are terminated by short domain swaps which themselves end within 5 A of the active sites of the partner molecules. Additionally, we show that the protein is indeed capable of circularizing RNA molecules in an ATP-dependent reaction. These structural and biochemical results provide an insight into the potential physiological roles of Pab1020.

Gastro-oesophageal reflux and gastric aspiration in lung transplant patients with or without chronic rejection

Acid gastro-oesophageal reflux (GOR) and gastric aspiration have been labelled as risk factors for chronic rejection bronchiolitis obliterans syndrome (BOS) after lung transplantation (LTx). The present study aimed to further characterise GOR (both acid and nonacid) and the degree of gastric aspiration in LTx recipients both with and without BOS. Impedance-pH recordings were used for GOR detection. Pepsin and bile acid levels were measured in bronchoalveolar lavage fluid (BALF). A total of 48% of patients had increased GOR, of which 27% had exclusively increased nonacid reflux. Cystic fibrosis patients had the highest prevalence of GOR. Pepsin was found in BALF of all patients and bile acids in BALF of 50% of the patients. Patients with BOS had neither increased GOR nor elevated pepsin in BALF. However, 70% of the patients with BOS had bile in BALF compared with 31% of stable patients. Proton pump inhibitor (PPI) treatment reduced acid reflux but did not affect nonacid reflux. Moreover, pepsin and bile levels in BALF were not reduced by PPI. One-half of the lung transplant patients had increased reflux, and nonacid reflux was common. Gastric aspiration occurred in most lung transplant patients. Pepsin was a more general marker and bile acids a more specific marker that might be associated with bronchiolitis obliterans syndrome. Proton pump inhibitor treatment did not prevent nonacid reflux and gastric aspiration.

Relevance of mild ineffective oesophageal motility (IOM) and potential pharmacological reversibility of severe IOM in patients with gastro-oesophageal reflux disease

BACKGROUND

Several studies showed high prevalence of ineffective oesophageal motility (IOM) in gastro-oesophageal reflux disease (GERD) and suggested an important role for ineffective oesophageal motility in increased acid exposure. However, impedance-manometric studies proposed that only severe ineffective oesophageal motility might affect oesophageal clearance.

OBJECTIVES

(i) To re-assess the relevance of mild IOM in GERD and (ii) to test the reversibility of IOM.

METHODS

Oesophageal motility, clearance and acid exposure were assessed in 191 GERD patients: 99 without IOM; 58 with mild IOM (30-80% ineffective contractions) and 34 with severe IOM (>80% ineffective contractions). In 30 patients with oesophagitis, the potential reversibility of IOM was evaluated with edrophonium intravenously.

RESULTS

Patients with mild IOM had identical oesophageal clearance and acid exposure in comparison with those without IOM. Patients with severe IOM had a higher probability of prolonged supine clearance and acid exposure [odds ratio: 2.88 (1.16-7.17); 2.48 (0.99-6.17)]. This effect was independent of the presence of hiatal hernia and male sex. Severe IOM could be transiently reverted in 55% of patients.

CONCLUSIONS

Mild IOM does not affect oesophageal clearance. Only severe IOM is associated with prolonged clearance and acid exposure, particularly in supine periods. The edrophonium test might be useful to predict severe IOM response to prokinetic medications.

Improved diagnosis of gastro-oesophageal reflux in patients with unexplained chronic cough

BACKGROUND

Symptoms, oesophageal pHmetry and proton pump inhibitor treatment are used for diagnosing gastro-oesophageal reflux-related cough. Weakly acidic reflux is now increasingly associated with reflux symptoms such as regurgitation or chest pain.

AIM

To study the association between weakly acidic reflux and cough in a selected, large group of patients with unexplained chronic cough.

METHODS

A total of 100 patients with chronic cough (77 'off' and 23 'on' a proton pump inhibitor) were studied using impedance-pHmetry for reflux detection and manometry for objective cough monitoring. Symptom Association Probability (SAP) Analysis characterized the reflux-cough association.

RESULTS

Acid reflux could be a potential mechanism for cough in 45 patients (with either heartburn, high acid exposure or +SAP for acid reflux). Weakly acidic reflux could be a potential mechanism for cough in 24 patients (with either increased oesophageal volume exposure, increased number of weakly acidic reflux or +SAP for weakly acidic reflux). Reflux could not be identified as a potential mechanism for cough in 31 patients.

CONCLUSION

A positive association between cough and weakly acidic reflux was found in a significant subgroup of patients with unexplained chronic cough. Impedance-pH-manometry identified patients in whom cough can be related to reflux that would have been disregarded using the standard diagnostic criteria for acid reflux.

Cloning, production, and purification of proteins for a medium-scale structural genomics project

The South-Paris Yeast Structural Genomics Pilot Project (http://www.genomics.eu.org) aims at systematically expressing, purifying, and determining the three-dimensional structures of Saccharomyces cerevisiae proteins. We have already cloned 240 yeast open reading frames in the Escherichia coli pET system. Eighty-two percent of the targets can be expressed in E. coli, and 61% yield soluble protein. We have currently purified 58 proteins. Twelve X-ray structures have been solved, six are in progress, and six other proteins gave crystals. In this chapter, we present the general experimental flowchart applied for this project. One of the main difficulties encountered in this pilot project was the low solubility of a great number of target proteins. We have developed parallel strategies to recover these proteins from inclusion bodies, including refolding, coexpression with chaperones, and an in vitro expression system. A limited proteolysis protocol, developed to localize flexible regions in proteins that could hinder crystallization, is also described.

Pichia pastoris is a valuable host for the expression of genes encoding membrane proteins from the hyperthermophilic Archeon Pyrococcus abyssi

We present here the experimental strategies, first results and identified bottlenecks of a structural genomics initiative on membrane proteins of the hyperthermophilic archaea Pyrococcus abyssi. Five ORFs coding for putative membrane proteins have been cloned and expressed in the methylotrophic Pichia pastoris expression system, using two different constructs, with or without the signal sequence alpha-mating factor of Saccharomyces cerevisiae. A c-myc epitope and 6 His codons were added at the 3'-end of the targeted genes to allow immunodetection of the recombinant proteins and to facilitate their further purification. We have selected at least one producer clone for each protein of interest and for almost every construction. All the membrane proteins were produced in Erlenmeyer flasks culture and in fed-batch cultivation for large-scale preparation. The proteins were detected in the membrane fractions of P. pastoris. Production efficiencies were relatively low in both production conditions but the quantities of biomass obtained during fed-batch cultivation have allowed us to collect sufficient amount of material for further purification. The proteins were extracted, solubilized and partially purified. Large-scale purification will be necessary for further structural work.