Biliary papillomatosis.

Biliary papillomatosis (BP) is a rare disorder of the biliary tract characterized by the presence of multiple papillary adenomas spread along the biliary tree. Although benign, it carries a significant risk of malignant transformation. Due to low sensitivity and specificity of conventional radiologic modalities, the diagnosis as well as estimation of disease extent is difficult. Endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreaticography (ERCP) are superior although direct peroral cholangioscopy (POC) is currently the most accurate diagnostic method. Mainly because it provides more detailed information and makes targeted histological diagnosis possible. The treatment of biliary papillomatosis consists of surgical resection, liver transplantation (LT) or a combination of both. Unfortunately, the recurrence rate after radical surgery without LT remains high due to the diffuse distribution of the disease.

Endoscopic therapy for Bouveret syndrome, illustrated by a case report.

Bouveret syndrome is an exceptionally rare form of gallstone ileus secondary to a bilioenteric fistula, through which a voluminous gallstone can migrate into the pylorus or duodenum, thereby causing gastric outlet obstruction. In order to increase awareness, we reviewed the clinical features, diagnostic tools and management options for this uncommon entity. We specifically focus on endoscopic therapeutic options, illustrated by a case of a 73 year old woman with Bouveret syndrome, where endoscopic electrohydraulic lithotripsy was successful in relieving gastroduodenal obstruction.

Umbilical hernia repair in patients with cirrhosis: who, when and how to treat.

PURPOSE: Hernia management in patients with cirrhosis is a challenging problem, where indication, timing and type of surgery have been a subject of debate. Given the high risk of morbidity and mortality following surgery, together with increased risk of recurrence, a wait and see approach was often advocated in the past. METHODS: The purpose of this review was to provide an overview of crucial elements in the treatment of patients with cirrhosis and umbilical hernia. RESULTS: Perioperative ascites control is regarded as the major factor in timing of hernia repair and is considered the most important factor governing outcome. This can be accomplished by either medical treatment, ascites drainage prior to surgery or reduction of portal hypertension by means of a transjugular intrahepatic portosystemic shunt (TIPS). The high incidence of perioperative complications and inferior outcomes of emergency surgery strongly favor elective surgery, instead of a "wait and see" approach, allowing for adequate patient selection, scheduled timing of elective surgery and dedicated perioperative care. The Child-Pugh-Turcotte and MELD score remain strong prognostic parameters and furthermore aid in identifying patients who fulfill criteria for liver transplantation. Such patients should be evaluated for early listing as potential candidates for transplantation and simultaneous hernia repair, especially in case of umbilical vein recanalization and uncontrolled refractory preoperative ascites. Considering surgical techniques, low-quality evidence suggests mesh implantation might reduce hernia recurrence without dramatically increasing morbidity, at least in elective circumstances. CONCLUSION: Preventing emergency surgery and optimizing perioperative care are crucial factors in reducing morbidity and mortality in patients with umbilical hernia and cirrhosis.

Erythema multiforme in the esophagus.

Erythema multiforme is an immune-mediated mucocutaneous disorder. Mucosal involvement usually affects the oral region, the genitals or the eyes. We report a case of esophagitis caused by erythema multiforme in a patient diagnosed with lung cancer. Esophageal manifestation in erythema multiforme is rarely seen. Besides esophagitis it can lead to esophageal strictures. Erythema multiforme is mostly triggered by infection or drugs but the association with malignancy has been described.

Endoscopic vacuum-assisted closure therapy for the treatment of oesophageal anastomotic leaks.

Persisting suture dehiscence with oesophageal anastomotic leaks after thoracic surgery is a difficult complication, especially when a surgical repair fails. We report here endoscopic vacuum-assisted closure therapy as a novel endoscopic treatment for the management of oesophageal anastomotic leaks. Endoscopic vacuum-assisted closure therapy is a minimally invasive method to treat anastomotic leakage by positioning an open-pored polyurethane sponge and a suction tube connected to a wound drainage system into the opening of the wound cavity. This multidisciplinary endoscopic and surgical approach is a successful therapy for the management of suture dehiscence with oesophageal anastomotic leaks after thoracic surgery or oesophageal perforations.

Primary syphilitic proctitis : case report and literature review.

Rectal ulcerations are an uncommon presentation of a primary syphilis infection. Anorectal syphilis is difficult to diagnose because of its often asymptomatic or atypical clinical presentation. It is important to consider sexually transmitted diseases (STD) in all patients presenting with rectal symptoms. A history of anal sexual intercourse should be made, especially in men having sex with men (MSM). Moreover, the possibility of a primary syphilis infection of the rectum should be considered. Endoscopic findings might be diverse, whereas a typical chancre can present as an anorectal ulcer associated with regional lymphadenopathy. It is important to consider other causes of anorectal ulcers, like other STD, inflammatory bowel disease (IBD) or even malignant causes. The diagnosis of anorectal syphilis is based on the combination of the clinical presentation, serology tests, endoscopic findings and biopsies. The cornerstone of the treatment is based on an intramuscularly administration of a long-acting preparation of penicillin (benzathine penicillin G).

Pneumomediastinum as a complication of esophageal intramural pseudodiverticulosis.

Dysphagia is a common complaint of patients seen at the outpatient clinic as well as at the emergency room. We report esophageal intramural pseudodiverticulosis (EIPD) as a cause of dysphagia that is less known by physicians and it is rarely described in the literature. EIPD is characterized by multiple, segmental or diffuse, flask-like outpouchings in the esophageal wall corresponding to dilated and inflamed excretory ducts of the submucosal esophageal glands. The underlying etiology remains unclear. Esophageal strictures, esophageal candidiasis and gastroesophageal reflux disease are often associated. The diagnosis can be made by upper gastrointestinal endoscopy, but barium esophagography is the modality of choice. Complications of EIPD are rare and include broncho-esophageal and esophagomediastinal fistula, pleural and pericardial effusion, abscesses, gastrointestinal bleeding from a web-like stenosis or esophageal perforation with pneumomediastinum. The treatment for EIPD should be directed towards treating underlying associated conditions and relieving symptoms rather than the pseudodiverticulosis itself.

Role of the carboxy-terminal phenylalanine in the biogenesis of outer membrane protein PhoE of Escherichia coli K-12.

Most bacterial outer membrane proteins contain a phenylalanine at their C terminus. It has been shown that this residue has an important role in the efficient and correct assembly of PhoE protein into the Escherichia coli outer membrane, since its substitution or deletion resulted in the accumulation of trypsin-sensitive monomers of this normally trimeric protein. Here, the role of the C-terminal Phe in the assembly of PhoE was studied in further detail. Immunocytochemical labelling on ultrathin cryosections revealed that a mutant PhoE protein that lacks the C-terminal Phe accumulates in the periplasm. However, when the expression levels of the altered species were reduced, the efficiency of outer membrane incorporation was increased and the lethal effects were alleviated. The role of the C-terminal Phe in protein folding, trimerization and outer membrane incorporation was further studied in vitro. Deletion of this residue interfered with the efficiency of the formation of an assembly-competent folded monomer, and the stability of this PhoE form was affected. The in vitro trimerization and insertion into outer membranes were not affected by the mutation.

Effect of different positively charged amino acids, C-terminally of the signal peptidase cleavage site, on the translocation kinetics of a precursor protein in Escherichia coli K-12.

Introduction of positively charged amino acids immediately downstream of the signal sequence in prokaryotic precursor proteins is known to affect the export process. However, it is not clear whether different positively charged amino acids affect the export process similarly. To investigate this, the glutamate at position +2 of outer membrane protein PhoE was substituted by arginine, lysine or histidine. Pulse-chase experiments revealed that the Lys and Arg residues at position +2 caused a reduced processing rate, and that the effect was markedly more severe in the case of the Arg residue. Trypsin accessibility experiments revealed that the accumulated precursors were present in the cytoplasm. Since the degree of the inhibitory effect corresponded to the pKa of the different positively charged amino acids, this suggests that the positively charged residues must be deprotonated during the secretory process.

Topology of PhoE porin: the 'eyelet' region.

A model for the topology of the PhoE porin has been proposed according to which the polypeptide traverses the outer membrane sixteen times mostly as amphipathic beta-sheets, thereby exposing eight loops at the cell surface. Until now, no evidence has been obtained for the surface exposure of the third loop. Recently, the structure of porin of Rhodobacter capsulatus has been determined. The proposed model of PhoE is very similar to the structure of the R. capsulatus porin, which has an 'eyelet' region, extending into the interior of the pore. The proposed third external loop of PhoE might form a similar 'eyelet' region. To determine the location of the predicted third external loop of PhoE, multiple copies of an oligonucleotide linker encoding an antigenic determinant of VP1 protein of foot-and-mouth disease virus (FMDV) were inserted. All hybrid proteins were properly inserted in the outer membrane. The monoclonal antibody MA11, directed against the linear FMDV epitope, was able to bind only to intact cells expressing a hybrid PhoE protein with at least three copies of the FMDV epitope present. Antibiotic sensitivity tests and single-channel conductance measurements revealed that the insertions influenced the channel size. These results are consistent with a location of the third loop of PhoE within the pore channel.

Carboxy-terminal phenylalanine is essential for the correct assembly of a bacterial outer membrane protein.

Bacterial outer membrane proteins are supposed to span the membrane repeatedly, mostly in the form of amphipathic beta-sheets. The last ten C-terminal amino acid residues of PhoE protein are supposed to form such a membrane-spanning segment. Deletion of this segment completely prevents incorporation into the outer membrane. Comparison of the last ten amino acid residues of other outer membrane proteins from different Gram-negative bacteria revealed the presence of a potential amphipathic beta-sheet with hydrophobic residues at positions 1 (Phe), 3 (preferentially Tyr), 5, 7 and 9 from the C terminus, in the vast majority of these proteins. Since such sequences were not detected at the C termini of periplasmic proteins, it appears to be possible to discriminate between the majority of outer membrane proteins and periplasmic proteins on the basis of sequence data. The highly conserved phenylalanine at the C termini of outer membrane proteins suggests an important function for this amino acid in assembly into the outer membrane. Site-directed mutagenesis was applied to study the role of the C-terminal Phe in PhoE protein assembly. All mutant proteins were correctly incorporated into the outer membrane to some extent, but the efficiency of the process was severely affected. It appears that both the hydrophobicity and the aromatic nature of Phe are of importance.

Tryptophan fluorescence study on the interaction of the signal peptide of the Escherichia coli outer membrane protein PhoE with model membranes.

The interaction of the signal peptide of the Escherichia coli outer membrane protein PhoE with different phospholipid vesicles was investigated by fluorescence techniques, using a synthetic mutant signal peptide in which valine at position -8 in the hydrophobic sequence was replaced by tryptophan. First it was established that this mutation in the signal sequence of prePhoE does not affect in vivo and in vitro translocation efficiency and that the biophysical properties of the synthetic mutant signal peptide are similar to those of the wild-type signal peptide. Next, fluorescence experiments were performed which showed an increase in quantum yield and a blue shift of the emission wavelength maximum upon interaction of the signal peptide with lipid vesicles, indicating that the tryptophan moiety enters a more hydrophobic environment. These changes in intrinsic fluorescence were found to be more pronounced in the presence of phosphatidylglycerol (PG) or cardiolipin (CL) than with phosphatidylcholine (PC). In addition, quenching experiments demonstrated a shielding of the tryptophan fluorescence from quenching by the aqueous quenchers iodide and acrylamide upon interaction of the signal peptide with lipid vesicles, a shielding in the case of acrylamide that was more pronounced in the presence of negatively charged lipids. Finally it was found that acyl chain brominated lipids incorporated into phospholipid bilayers were able to quench the tryptophan fluorescence of the signal peptide, with the quenching efficiency in CL vesicles being much higher than in PC vesicles. The results clearly demonstrate that the PhoE signal peptide interacts strongly with different lipid vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of Neisseria meningitidis mutants deficient in class 1 (porA) and class 3 (porB) outer membrane proteins.

The class 1 major outer membrane protein of Neisseria meningitidis is a serious candidate for a meningococcal vaccine. To facilitate studies on the function of this protein, mutants were isolated that lacked this protein or the structurally related class 3 protein. These mutants were obtained by using the antibody-dependent bactericidal action of the complement system. The class 1 protein-deficient strain grew normally in vitro, whereas growth of the class 3 protein-deficient strain was slightly retarded. The class 3 protein-deficient strain displayed increased resistance to the antibiotics tetracycline and cefsulodin, which is consistent with the proposed role of the protein as a pore-forming protein. The class 1 protein was purified to homogeneity from the class 3 protein-deficient strain. Lipid bilayer experiments revealed that this protein also formed pores. The class 1 protein pores were cation selective.

One single lysine residue is responsible for the special interaction between polyphosphate and the outer membrane porin PhoE of Escherichia coli.

Site-directed mutagenesis was performed with the phosphate starvation-inducible outer membrane porin PhoE of Escherichia coli K-12 to study the molecular basis of its anion selectivity. Lysines 18, 29, 64, and 125 were replaced by glutamic acids, and the properties of the mutant porins were investigated in in vivo and in vitro experiments. Lipid bilayer experiments showed that all these mutations had no influence on the pore structure because PhoE and the mutants had the same single channel conductance in KCl solution. Selectivity measurements revealed that the mutations changed the ionic selectivity of PhoE, but the change was dependent on the location of the lysine. Replacement of Lys18 and Lys29 by glutamic acid had a relatively small influence. The effect of the Lys64 substitution was somewhat larger, and the effect of the replacement of Lys125 resulted in the most drastic change in selectivity and in the loss of the interaction of PhoE with polyphosphate, whereas the replacement of the other lysines had no effect on the polyphosphate interaction behavior. The results are consistent with the assumption that the charge spot in PhoE consists of only 1 lysine per monomer, located in position 125 of the primary sequence and probably close to the pore interior.

Topology of outer membrane pore protein PhoE of Escherichia coli. Identification of cell surface-exposed amino acids with the aid of monoclonal antibodies.

Monoclonal antibodies which recognize the cell surface-exposed part of outer membrane protein PhoE of Escherichia coli were used to select for antigenic mutants producing an altered PhoE protein. The selection procedure was based on the antibody-dependent bactericidal action of the complement system. Using two distinct PhoE-specific monoclonal antibodies, seven independent mutants with an altered PhoE protein were isolated. Among these seven mutants, five distinct binding patterns were observed with a panel of 10 monoclonal antibodies. DNA sequence analysis revealed the following substitutions in the 330-residue-long PhoE protein: Arg-201----His (three isolates), Arg-201----Cys, Gly-238----Ser, Gly-275----Ser and Gly-275----Asp. It is argued that amino acid residues 201, 238, and 275 are most likely directly involved in antibody binding and, therefore, exposed at the cell surface. Together with Arg-158, which was previously shown to be cell surface exposed as it is changed in phage TC45-resistant phoE mutants, these four positions show a remarkably regular spacing, being approximately 40 residues apart. A model is suggested in which the PhoE polypeptide repeatedly traverses the outer membrane in an antiparallel beta-pleated sheet structure, exposing eight areas to the outside which are all separated by approximately 40 residues.