Mechanical fractionation reveals structural requirements for enteropathogenic Escherichia coli Tir insertion into host membranes

Enteropathogenic Escherichia coli (EPEC) inserts its receptor for intimate adherence (Tir) into host cell membranes by using a type III secretion system. Detergents are frequently used to fractionate infected host cells to investigate bacterial protein delivery into mammalian cells. In this study, we found that the Triton X-100-soluble membrane fraction from EPEC-infected HeLa cells was contaminated with bacterial proteins. We therefore applied a mechanical method of cell lysis and ultracentrifugation to fractionate infected HeLa cells to investigate the biology and biochemistry of Tir delivery and translocation. This method demonstrates that the translocation of Tir into the host cell membrane requires its transmembrane domains, but not tyrosine phosphorylation or binding to Tir's ligand, intimin.

Absence of hepatitis C genome in semen of infected men by polymerase chain reaction, branched DNA and in situ hybridization

BACKGROUND/AIMS

The presence or absence of hepatitis C virus (HCV) RNA in the semen of infected man remains controversial, mainly due to technical difficulties associated with nucleic acid detection. The aims of this study were to assess the presence of HCV RNA in spermatozoa and in seminal fluid using different polymerase chain reaction (PCR)- and non-PCR-dependent methods and, in the case of HCV presence, to correlate this detection with the viraemia.

METHODS

Serum and semen from 25 chronically infected hepatitis C patients were studied. The semen was separated into spermatozoa and seminal fluid and HCV RNA was analysed in the two fractions using RT-PCR and branched DNA. The presence of HCV RNA in pelleted cells was also assessed using in situ hybridization.

RESULTS

All three approaches failed to demonstrate HCV RNA in semen. The presence of an inhibitor of the PCR was demonstrated in seminal fluid but not in spermatoza.

CONCLUSION

Our results confirmed the lack of detection of HCV RNA in semen by PCR- and non-PCR-dependent techniques and support the view that viral contamination in semen remains, if present, at a very low level. Nevertheless, epidemiological studies are required to definitively assess the absence of sexual transmission of HCV

[Central nervous system demyelinating disease following hepatitis B vaccination with GenHevac B. Review of ten years of spontaneous notifications (1989-1998)]

OBJECTIVES

To describe and analyze spontaneous reports of central nervous system (CNS) demyelinating disease including multiple sclerosis, following vaccination with GenHevac B vaccine, from 1989 to December 31, 1998.

METHODS

Descriptive analysis of adverse event reports in the vaccinated population, including the number of cases of CNS demyelinating disease, their frequencies, their dates of onset in relation to dates of report and their distribution according to age, sex and the number of injections. A Kaplan-Meier curve was used to analyze the time period between the last dose of vaccine and the onset of CNS demyelinating disease.

RESULTS

Overall, 187 cases of CNS demyelinating disease were spontaneously reported, (0.54 reports per 100,000 doses of GenHevac B distributed). The average time period between the occurring date of onset of the disease and its subsequent report was 24 months. The average age of onset was 31.7 years old and 73% of cases were women. The time between the last dose of vaccine and the onset of disease was regularly distributed from 1 day to 5 years (median: 60 days).

CONCLUSION

These results, together with available clinical, epidemiological data regarding multiple sclerosis, do not suggest a causal relationship between CNS demyelinating disease and vaccination with GenHevac B.

Objective assessment of the contribution of each diagnostic test and of the ordering sequence in jaundice caused by pancreatobiliary carcinoma

BACKGROUND

Computer-assisted diagnostic systems are not substantially more accurate than the clinician in the differential diagnosis of jaundice but may help in optimal selection and sequencing of tests. The present study aimed to assess with an electronic diagnostic tool the pattern of ordering tests and the diagnostic contribution and related financial cost of each test in jaundiced patients with pancreatobiliary carcinoma, in an effort to make the clinician's diagnostic behaviour more efficient and economical.

METHODS

Clinical and diagnostic test data were prospectively gathered from 356 jaundiced patients with pancreatobiliary carcinoma and entered in a Bayesian diagnostic programme. The test results were added to the existing diagnostic evidence, and the programme calculated the diagnostic contribution of each test.

RESULTS

A total of 1804 diagnostic tests were ordered. Quantitative assessment of the diagnostic contribution of each test showed that percutaneous transhepatic cholangiography and computed tomography were associated with the highest provision of information. The most cost-effective tests were ultrasonography and liver function tests.

CONCLUSIONS

It is possible to determine objectively the diagnostic contribution of each test in establishing the diagnosis of pancreatobiliary carcinoma. The observed physician behaviour in ordering the various diagnostic tests might be improved with regard to its efficacy and its cost-effectiveness profile.

Comparison of mobile lithotripters at one institution: healthtronics lithotron, Dornier MFL-5000, and Dornier Doli

BACKGROUND AND PURPOSE

Extracorporeal shockwave lithotripsy (SWL) has replaced most surgical and endourologic procedures for upper urinary tract stone disease. Our institution contracted with mobile lithotripter companies to provide SWL. We reviewed the outcomes of 50 patients treated on each machine with regard to efficacy, complications, and retreatment rates.

PATIENTS AND METHODS

One hundred fifty patients over 21 years of age were treated at Ochsner Foundation Hospital from April 1995 through June 1998. All stones were in either the kidney or the upper ureter, and all were <20 mm. Three mobile lithotripters-the Dornier MFL-5000 (4/95-9/96), the Dornier Doli (9/96-11/97), and the HealthTronics Lithotron (12/97-4/98)-were each used to treat 50 patients. Conscious monitored intravenous sedation was used in all patients. Post-treatment evaluations were made at 2 weeks, 1 month, and 3 months.

RESULTS

A successful outcome (stone free or fragments <4 mm) was achieved in 72% (MLF-5000), 68% (Doli), and 80% (Lithotron) of patients (P = 0.39). Treatments that were followed by retreatments or other further procedures (ureteroscopy or percutaneous nephrolithotomy) were counted as failures. The retreatment rate was 10%, 22%, and 10%, respectively. There were three significant complications with the Doli unit: two large perirenal hematomas (4%) and one delayed splenic rupture in a patient with a history of pelvic surgery that necessitated transfusions and urgent splenectomy. The minor complication rates with all three lithotripters were similar to those reported in the literature. The three-month efficiency quotients were 0.55 for the Lithotron and MFL-5000 and 0.41 for the Doli.

CONCLUSIONS

Statistically equivalent success rates were achieved with all three machines. The electromagnetic unit (Doli) had higher rates of retreatment and significant complications than the electrohydraulic lithotripters (MFL-5000, Lithotron).

[Why we prefer the thin layer technique to conventional Pap smears. A double-blind study of 473 specimens]

The study evaluated the feasibility of a thinlayer technique on a routine basis for cervical smears and compared 473 ThinPrep preparations to the matched conventional Papsmears. The interpretation was double-blind and performed according to the Bethesda system. A consensus was established in discordant cases. The technique was easily mastered by gynecologists and technicians. Main advantages of the thinlayer technique were: a low number (1%) of unsatisfactory samples; a constant quality; homogeneity of cell distribution; the disappearance of problems of interpretation due to fixation or smear artifacts, red cells, polymorphs; a more precise interpretation, a firmer diagnosis; less visual fatigue; a shorter time of interpretation; the possibility of preparing more slides and performing special techniques on the same specimen. Main disadvantages were a higher cost and a necessary period of learning for cytologists.

Identification of the intimin-binding domain of Tir of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) attaches intimately to mammalian cells via a bacterial outer membrane adhesion molecule, intimin, and its receptor in the host cell membrane, Tir. Tir is a bacterial protein translocated into the host cell membrane and tyrosine phosphorylated after insertion. Tir-intimin binding induces organized actin polymerization beneath the adherent bacteria, resulting in the formation of pedestal-like structures. A series of Tir deletion derivatives were constructed to analyse which Tir domains are involved in intimin binding. We have localized the intimin-binding domain (IBD) of Tir using a yeast two-hybrid system and a gel-overlay approach to a region of 109 amino acids that is predicted to be exposed on the surface of the plasma membrane. A truncated Tir protein lacking this domain was translocated to the host cell membrane and tyrosine phosphorylated, but failed to bind intimin or to induce either actin polymerization or Tir accumulation beneath the bacteria. These results indicate that only a small region of Tir is needed to bind intimin and support the predicted topology for Tir, with both N- and C-terminal regions in the mammalian cell cytosol. They also confirm that Tir-intimin interactions are needed for cytoskeletal organization. We have also identified N-terminal regions involved in Tir stability and Tir secretion to the media.

Enteropathogenic Escherichia coli: a pathogen that inserts its own receptor into host cells

Enteropathogenic Escherichia coli (EPEC) is a major cause of infant diarrhea, killing hundreds of thousands of children per year worldwide. Intimate attachment to the host cell leading to the formation of actin-rich pedestals beneath the adhering bacteria is an essential feature of EPEC pathogenesis. EPEC attaches to host cells via the outer membrane adhesin, intimin. It was recently shown that EPEC inserts its own receptor for intimate adherence, Tir (translocated intimin receptor) into the host cell membrane. The focus of this review is on the discovery and characterization of this novel receptor, and our current understanding of its role in pedestal formation. Gram-negative bacterial secretion systems, including type III secretion systems, are reviewed and discussed in the context of Tir delivery into the host cell membrane. The relationship and relevance of in vitro models compared to the actual in vivo situation is essential to understanding disease. We have critically reviewed the use of animal models in studying EPEC infection. Elucidating the function of Tir will contribute to our understanding of how EPEC mediates disease.

Protein translocation: delivering virulence into the host cell

A wide variety of plant and human bacterial pathogens use a specialized 'type III' protein secretion system to deliver virulence factors into host cells. Appendage-like surface structures have recently been identified on several bacterial pathogens and there are indications that these may be conduits for virulence factor delivery.

[Familial varices of the colon. Report of four cases]

We report four cases of ileo-colonic varices in one family. This congenital disease is uncommon with only 21 cases described in the literature. Recurrent digestive tract bleeding is the most common manifestation, but varices can be asymptomatic. Digestive endoscopy leads to the diagnosis. The diagnosis of familial colonic varices can be considered when colonic varices occur in several members of a family with no evident cause, particularly portal hypertension or venous thrombosis. No treatment is usually necessary except when major or recurrent bleeding indicates surgical resection. These malformations are classified as vascular ectasia in the subgroup of cavernous haemangiomas.

Characterization of two cDNA clones which encode O-methyltransferases for the methylation of both flavonoid and phenylpropanoid compounds

Enzymatic O-methylation of phenylpropanoid and flavonoid compounds is believed to be catalyzed by distinct classes of O-methyltransferases [EC 2.1.1.6x]. The O-methylated derivatives of phenylpropanoids and flavonoids play an important role in lignification and as antimicrobial compounds, respectively. Two cDNA clones, OMT1 and OMT2, which differ in three amino acid residues were isolated and characterized from the semiaquatic freshwater weed Chrysosplenium americanum (Saxifragaceae). These two novel cDNA clones encode enzymes which catalyze the 3'-O-methylation of the flavonoid aglycones luteolin and quercetin, although they also catalyze the efficient 3/5-O-methylation of the phenylpropanoids caffeic and 5-hydroxyferulic acids, respectively. Both recombinant proteins were partially purified from an Escherichia coli expression system and their kinetic parameters were compared using two flavonoids and two phenylpropanoids as substrates. Although both gene products methylate caffeic acid and 5-hydroxyferulic acid to a similar extent, they exhibit a threefold higher affinity for and a four- to sixfold increase in turnover of flavonoid compounds. The gene product of OMT1 accepts the flavonoid substrates luteolin and quercetin for methylation at a higher rate than that of OMT2, as indicated by a two- to threefold increase in its Vmax values and turnover ratios. The fact that C. americanum accumulates a variety of highly methylated flavonols and exhibits little lignification suggests that these two flavonoid OMT clones have retained their ability to O-methylate phenylpropanoids as well. These results are discussed in relation to differences in the amino acid sequences of these two clones, as well as with other O-methyltransferases, and the evolutionary divergence of these genes in plants.

Effect of common organic solvents on in vitro cytochrome P450-mediated metabolic activities in human liver microsomes

In this study, we report the effect of methanol, dimethyl sulfoxide (DMSO), and acetonitrile on the cytochrome P450 (P450)-mediated metabolism of several substrates in human liver microsomes: phenacetin O-deethylation for P4501A2, coumarin 7-hydroxylation for P4502A6, tolbutamide hydroxylation for P4502C8/2C9, S-mephenytoin 4'-hydroxylation for P4502C19, dextromethorphan O-demethylation for P4502D6, chlorzoxazone 6-hydroxylation for P4502E1, and testosterone 6beta-hydroxylation for P4503A4. DMSO was found to inhibit several P450-mediated reactions (2C8/2C9, 2C19, 2E1, and 3A4) even at low concentrations (0.2%). There was no measurable effect on the catalytic activity of the various P450s when methanol was present at levels </=1%, except for P4502C8/9 and 2E1. Acetonitrile did not noticeably change the catalytic activity of the P4502C8/2C9, 2C19, 2D6, and 2E1 enzymes at concentrations </=1%. It was found that the content level of the organic solvents should be kept lower than 1% because, for all three solvents, a concentration of 5% strongly affected the metabolism of the various probes. These findings should be taken into consideration when designing in vitro metabolism studies of new chemical entities.

In vitro comparison of cytochrome P450-mediated metabolic activities in human, dog, cat, and horse

As domestic animals such as cat, horse, and dog increasingly become the clinical targets for drug discovery programs, the need to understand how these animals metabolize xenobiotics becomes more important. In the present study, substrates and inhibitors that were reported to be selective for particular P450 isozymes were used as probes to study in vitro metabolism in horse, dog, cat, and human liver microsomes. Seven selective catalytic activity markers for cytochrome P450-mediated reactions were measured: phenacetin O-deethylase (P4501A1/2), coumarin 7-hydroxylase (P4502A6), tolbutamide hydroxylase (P4502C8/9), S-mephenytoin 4'-hydroxylase (P4502C19), dextromethorphan O-demethylase (P4502D6), chlorzoxazone 6-hydroxylase (P4502E1), and testosterone 6beta-hydroxylase (P4503A4). Metabolic activity was found in every species with each substrate. Under the conditions of this study, it was observed that no one species was more active for any given substrate. However, rather large interspecies differences were observed. There was no marked sex difference in the way the various species metabolized the different substrates. The effect of selective P450 inhibitors on the various activities was tested with furafylline (P4501A2), mouse monoclonal antibody inhibitory to CYP2A6, sulfaphenazole (P4502C9), tranylcypromine (P4502C19), quinidine (P4502D6), diethyldithiocarbamate (P4502E1), and troleandomycin (P4503A4). In most cases, these inhibitors were effective to varying degrees against the activity seen in horse, dog, and cat liver microsomes. However, even at high concentrations, furafylline did not inhibit phenacetin O-deethylase activity in cat and troleandomycin did not affect testosterone 6beta-hydroxylase activity in horse. Sulfaphenazole was not tested in dog and cat because of the low tolbutamide hydroxylase activity. Overall, these results show that there are also large interspecies differences in the way the selective P450 inhibitors affect the in vitro metabolism of the various substrates in horse, dog, and cat liver microsomes.

Circadian rhythm in the torque developed by elbow flexors during isometric contraction. Effect of sampling schedules

Time-dependent changes in elbow flexion torque have been documented according to two different sampling schedules. Seven physical education students took part in the first series of experiments, and 7 other similar subjects in the second. In both sets of experiments, the subjects performed isometric contractions: maximal and submaximal at 90 degrees in the first experiments and maximal at different angular positions in the second. After a 30-minute rest period, the torque developed was measured at 00:00, 06:00, 09:00, 12:00, 15:00, 18:00, and 21:00 h on the day of the experiment. These subjects remained in the laboratory for 24 h. In the second series of experiments, the torque developed was measured at 01:00, 05:00, 09:00, 13:00, 17:00, and 21:00 h over the subsequent 6 days with only one test session per day. In this case, there was an interval of 20 h between two successive test sessions. In the first experiment, a significant time-of-day effect was observed for the torque of the elbow flexors under isometric conditions with an acrophase at 17:58 h. The 24 h normalized mean score was 92.85% with an amplitude of 7.63% of the daily mean. In the second series of experiments, there was evidence of a circadian rhythm in the torque developed by the elbow flexors at every angle position, especially at 90 degrees, the angle investigated in the first set of experiments. The peak torque was calculated to have occurred at 17:55 h. The amplitude of the rhythm was equal to 6.99% of the daily mean. There were no statistically significant differences in the characteristics of the circadian rhythm observed between the two experimental designs. We concluded that an experiment extending over several days could be employed to evaluate circadian rhythms in muscular activity reliably.

Effects of aluminum exposure on behavioral parameters in the rat

Adult rats were treated by intraperitoneal injection of aluminum gluconate for 3 months. Rats were submitted to the radial maze test to determine the influence of chronic aluminum intoxication on cognitive and noncognitive behavioral processes. Both learning abilities (working memory and reference memory) and rapidity (time spent to respond and to master a trial) were analyzed. Aluminum concentration was evaluated in the brain, serum, and liver to assess aluminum body burden. While hippocampus and neocortex showed a significant increase in aluminum concentration, aluminum treatment did never affect the animal's performance during cue learning or when the insert cues were removed. The only behavioral difference observed was a decrease in rapidity: both the total time to finish a trial and the latency to make the first choice were lengthened in aluminum-intoxicated rats.

Early operation for severe corrosive injury of the upper gastrointestinal tract

OBJECTIVE

To describe our experience of treating severe corrosive burns of the upper gastrointestinal (GI) tract.

DESIGN

Open study.

SETTING

Teaching hospital, France.

SUBJECTS

18 patients who had swallowed an alkaline substance (caustic soda in 10 cases) and 4 who had swallowed either hydrochloric or sulphuric acid.

INTERVENTIONS

Endoscopy was done a mean of 4 hours after the substance had been swallowed. 10 patients underwent oesophagogastrectomy without thoracotomy.

MAIN OUTCOME MEASURES

Morbidity and mortality.

RESULTS

4 of the 10 patients died and 3 developed postoperative complications. Of the 12 patients treated by feeding jejunostomy 7 developed stenosis that required operation and 3 developed stenosis that responded to dilatation. None of the 12 died.

CONCLUSIONS

Early oesophagoscopy allowed optimal management. Patients died if they swallowed more than 60 ml of a strong alkaline substance. When patients are treated conservatively about half will develop stenoses that require operation.

cDNA cloning and characterization of a 3'/5'-O-methyltransferase for partially methylated flavonols from Chrysosplenium americanum

Enzymatic O-methylation of plant secondary metabolites is an important mechanism for the inactivation of reactive hydroxyl groups and for the modification of their solubility. A cDNA clone (pFOMT3') encoding the gene for the 3'/5'-O-methylation of partially methylated flavonols was isolated from Chrysosplenium americanum (Saxifragaceae). We used a PCR fragment obtained with degenerate oligonucleotides designed from conserved regions of various O-methyltransferases (OMTs). The pFOMT3' cDNA sequence shows about 67-85% similarity to other plant OMT sequences. The recombinant protein expresses strict specificity for positions 3'/5' (meta) of partially methylated flavonols, but does not accept quercetin or caffeic acid for further methylation. Southern blot analysis of the genomic DNA probed with an OMT sequence suggests the presence of a number of related genes in this species, consistent with the multiple enzymatic methylations involved in the biosynthesis of polymethylated flavonols in this plant.

Genetic heterogeneity between type 1a and type 1b insulin-dependent diabetes mellitus: HLA class II and TAP gene analysis

The aim of this study was to compare the genetic susceptibility linked to the HLA Class II region genes of the Major Histocompatibility Complex in isolated insulin-dependent diabetes mellitus (1a-IDDM) and insulin-dependent diabetes mellitus associated with another autoimmune endocrinopathy (1b-IDDM). HLA genes DRB1, DQA1 and DQB1 were studied at the genomic level, as well as genes TAP1 and TAP2. One hundred and seventy-nine 1a-IDDM diabetic patients were compared with 83 1b-IDDM patients. While it appeared that common genetic traits characterize diabetes regardless of the subtype (1a or 1b), certain features differentiate the two forms of IDDM. Extending the analysis of risk haplotypes DRB1*03 and DRB1*04 to TAP genes elicited a difference between 1a-IDDM and 1b-IDDM patients. Haplo-type DRB1*03 was thus characterized in 1a-IDDM patients by a lower frequency of alleles TAP1-B (13.5%) and TAP2-B (16.2%), not found in 1b-IDDM patients (33.3% for each allele). Likewise, haplotype DRB1*04 is characterized in 1b-IDDM patients by a lower frequency of alleles TAP1-C (4.0%) and TAP2-B (8.0%) than in 1a-IDDM patients (22.2% and 25.9%, respectively). In total, this study showed that extending the characterization of HLA Class II haplotypes to TAP genes discriminates between the forms of diabetes restricted to a specific pancreatic affection and those reflecting a wider autoimmune disorder affecting several organs.

Molecular mapping of a Yq deletion in a patient with normal stature

The proximal long arm of the Y chromosome probably contains a gene (GCY) involved in stature determination. Recent reports have proposed the critical region extends from interval 4B to interval 5G (or 5E). In the present study, the deletion breakpoint in a male adult patient of normal height with a 46,X,del(Yq) karyotype was defined by the use of sequence-tagged site markers. The breakpoint was found between sY78 (interval 4B) and sY79 (interval 5A). The existence of a normal stature in this patient suggests that the growth determinant is proximal to sY79, therefore probably located in interval 4B or in proximal interval 5A of the Y chromosome.

Impact of various handling and storage conditions on quantitative detection of hepatitis C virus RNA

BACKGROUND/AIMS

Both HCV RNA viral load and HCV genotype have been described as important predicting factors determining the response to interferon in chronic hepatitis C. To investigate whether processing and storage conditions might influence the stability and could alter the concentration of the HCV RNA in serum, quantification of HCV RNA was performed by branched DNA assay.

METHODS

We studied serum samples obtained from seven patients with histologically proven chronic hepatitis C. These were subjected to the following physical conditions: (1) immediate quantification, (2) storage at room temperature for 5 days, (3) storage at 4 degrees C for 5 days, (4) storage at -20 degrees C for 5 days, (5) storage at -80 degrees C for 5 days, (6) five freeze-thaw cycles, (7) blood unspun for 4 h at room temperature then centrifuged and stored at -80 degrees C for 5 days, (8) storage at 4 degrees C for 6 months, (9) storage at -20 degrees C for 6 months, (10) storage at -80 degrees C for 6 months.

RESULTS

A loss of 100% HCV RNA titers was observed after storage at RT for 5 days and then storage at 4 degrees C for 6 months. A surprising decrease of HCV RNA titer (15.6%) was observed in sera stored for 5 days at -20 degrees C. Five freeze-thaw cycles resulted in a 16% decrease of the HCV RNA level. When centrifugation was performed after a 4 h delay at room temperature, a significant loss of HCV RNA titers of 29.5% was observed. Long-term stability (6 months) was observed at -80 degrees C with a slight loss of about of 10% HCV RNA titers, but a significant decrease in HCV RNA of 23% was observed at -20 degrees C. The reproducibility of the bDNA assay on five patient samples was performed eight times in duplicate and showed an average coefficient of variation of 9.1%.

CONCLUSIONS

These data confirm the importance of storage and handling in measuring the amount of HCV RNA in clinical samples.