Reversible shift in the alpha-, beta- and gamma-proteobacteria populations of drinking water biofilms during discontinuous chlorination.

As disinfection strategies could support a shift of some bacterial populations, the biodiversity of drinking water biofilms depending on the disinfectant concentrations was explored. The effect of different chlorine sequences applied for several weeks (0.1-0.4-0.1 mg Cl(2)L(-1) or vice versa) was tested on the abundance of the alpha-, beta- and gamma-proteobacteria populations, used as indicators of changes in bacterial populations within drinking water biofilms. Using dynamic (industrial pilot) and batch (bench scale) conditions, our work demonstrated the ability of the 3 proteobacteria subclasses to re-organize following discontinuous chlorinations. The beta- and gamma-proteobacteria subclasses were favoured by high free residual chlorine concentrations (0.4 mg Cl(2)L(-1)) while alpha-proteobacteria population was sensitive to this oxidant level. The proteobacteria population shifts within the biofilm exposed to discontinuous chlorination were reversible. The resilience of the biofilm proteobacteria populations exposed to oxidant stress questioned the emergence of bacterial population less sensitive to chlorine.

Review article: gastro-oesophageal reflux disease and psychological comorbidity.

BACKGROUND: A growing number of studies have shown the impact of psychological comorbidities on gastro-oesophageal reflux disease (GERD) patients' symptom reports and healthcare-seeking behaviour. AIM: To review the reported relationship between GERD and psychological comorbidity. METHODS: Review of the literature on GERD and psychological comorbidity. RESULTS: Psychological comorbidity is common among GERD patients and appears to afflict all GERD phenotypes. Sexual and physical abuse is also common in GERD patients. Stress enhances perception of oesophageal acid exposure. Treatment for GERD, especially in those who are not responsive to antireflux treatment, may require further evaluation for psychological comorbidity. CONCLUSIONS: Psychological comorbidity is very common in GERD patients and is likely to play an important role in response, or failure of response, to proton pump inhibitor treatment.

Coliform culturability in over- versus undersaturated drinking waters.

The culturability of Escherichia coli in undersaturated drinking water with respect to CaCO3 (corrosive water) or in oversaturated water (non-corrosive water) was tested in different reactors: glass flasks (batch, "non-reactive" wall); glass reactors (chemostat, "non-reactive" wall) versus a corroded cast iron Propella reactor (chemostat, "reactive" wall) and a 15-year-old distribution system pilot (chemostat, "reactive" wall with 1% corroded cast iron and 99% cement-lined cast iron). The E. coli in E. coli-spiked drinking water was not able to maintain its culturability and colonize the experimental systems. It appears from our results that the optimal pH for maintaining E. coli culturability was around 8.2 or higher. However, in reactors with a reactive wall (corroded cast iron), the decline in E. coli culturability was slower when the pH was adjusted to 7.9 or 7.7 (i.e. a reactor fed with corrosive water; pHpHs). We tentatively deduce that corrosion products coming from chemical reactions driven by corrosive waters on the pipe wall improve E. coli culturability.

Release of organic matter in a discontinuously chlorinated drinking water network.

The effects of discontinuous chlorination on the characteristics of the water in a pilot drinking water distribution network were investigated. The release or consumption of organic matter (as dissolved organic carbon, DOC) following chlorination and non-chlorination periods were estimated, as were changes in bacterial cell production. In each unchlorinated network 0.3 mg DOCl(-1) was consumed and the average cell production was approximately 1.3 x 10(5) cells ml(-1). In discontinously chlorinated networks (chlorine treatment: 3.3 mg Cl2l(-1), chlorine residual: 0.1 mg Cl2l(-1)) the DOC release (DOCout-DOCin) was between 0.1 and 0.2 mg Cl(-1). Biomass production (cells(out)-cells(in)) during this chlorination period was lower (approximately 2 x 10(4) cells ml(-1)). The delay before DOC was released in chlorinated networks appeared to be less than 24 h, which corresponds to one hydraulic residence time. Likewise, when chlorination was stopped, 24 h or less were required before an efficient DOC removal was resumed. When chlorination was prolonged the observed release of DOC was progressively reduced from 0.2 mg l(-1) to zero, thus after 6 weeks of continuous chlorination the DOCin was equivalent to the DOCout.

Relationship between coliform culturability and organic matter in low nutritive waters.

The objective of this work was to investigate the behaviour of coliform bacteria in specific low nutritive waters conveying organic fractions from different origin of which an unknown part is likely to pass through the treatment barrier. For this purpose, we studied the growth (microscopic counting) and the culturability (count on nutritive medium) of ten coliform bacteria species as a function of the amount of organic matter in a river water collected after a period of heavy rain and in an algal bloom water. Assays were carried out in the presence of autochthonous heterotrophic bacteria from the Nancy (France) drinking water, with variable concentrations of dissolved organic carbon (DOC) representative of drinking waters (0.5-1.5 mg l(-1) for diluted river water samples and 1.3-2.5 mg l(-1) for diluted algal bloom water samples). Bacterial growth was measured in the two types of water, regardless of the initial concentration of DOC. We found that coliform bacteria lost their culturability in both sample series, and that the lower the initial DOC concentration the more rapidly the culturability was lost. The quantity of DOC consumed by the bacteria in the two water types (0.03-0.13 mg l(-1) in river water and 0.77-1.29 mg l(-1) in algal bloom water) and the resulting consequences on bacterial behaviour suggested that bloom water contains algal organic compounds that are antagonistic to the growth and/or the culturability of coliform bacteria. Organic matter thresholds, beyond which coliform bacteria are unlikely to keep their culturability, have not been determined experimentally. Indeed, at the end of the assays some culturable coliform bacteria were systematically detected in both types of water. Enterobacter cloacae was the predominant species. Thus, during these adverse events the probability of coliform occurrence can be considered as high in treated water.

Safety of laparoscopic splenectomy in elderly patients with idiopathic thrombocytopenic purpura.

Laparoscopic splenectomy (LS) for immune thrombocytopenic purpura (ITP) is very successful. However, the safety of LS in older patients who have less cardiac and pulmonary reserve has not been studied. Our objective was to compare results of LS in elderly and younger patients with ITP. LS performed for ITP between 1992 and 1999 were studied. Perioperative data were collected concurrently. Follow-up was obtained by chart review and phone interview. Groups were arbitrarily divided: Group A, age > or =70; group B, age <70. Main outcome measures were platelet response, duration of operation, hospitalization, blood loss, and complications were compared using t test and Chi-square analyses. Group A had more comorbid conditions (80% vs 28%, P = 0.04). Operative time (80 vs 119 minutes, P = 0.23), estimated blood loss (156 vs 189 cm3, P = 0.62), and hospitalization (3.6 vs 2.8 days, P = 0.23) were similar for both groups. Although group B had significantly more patients with an early platelet response (70% vs 97%, P = 0.02), there was no difference in platelet response at long-term follow-up (70% vs 84%, P = 0.22). Long-term follow-up was completed on 87 per cent of patients at an average of 43 months postoperatively. We conclude that LS is safe and effective in elderly patients with ITP.

Gastroesophageal disease and nausea: does fundoplication help or hurt?

HYPOTHESIS: Nausea associated with gastroesophageal reflux disease is cured by laparoscopic Nissen fundoplication (LNF). DESIGN: Prospective cohort study of unselected patients who underwent LNF from January 1, 1995, through March 31, 1999. Patients were followed up by a physician for 6 to 36 months. SETTING: A large community teaching hospital. PATIENTS: One hundred consecutive patients with gastroesophageal reflux disease who underwent LNF; all patients were followed up. Patients were grouped according to the presence (group A, n = 33) or absence (group B, n = 67) of preoperative nausea. Interventions were LNF, esophageal manometry, 24-hour pH monitoring, and nuclear gastric emptying studies. MAIN OUTCOME MEASURES: Resolution of symptoms after LNF. RESULTS: Nausea was the most common atypical symptom of gastroesophageal reflux disease, occurring in 33 patients (33%). There were no differences in esophageal manometry or 24-hour pH results between groups. There was a female preponderance in group A (55% vs 33%; P = .003). Patients in group A had a higher prevalence of preoperative dysphagia (P = .02). Patients with persistent postoperative nausea had a higher prevalence of cough (P = .003) and dysphagia (P = .009). The LNF was more effective in reducing heartburn (95% reduction) and regurgitation (95% reduction) than cough and dysphagia (60% reduction). There was a 79% reduction in the number of patients with nausea (33 to 7; P<.001). CONCLUSION: Laparoscopic Nissen fundoplication is effective in eliminating nausea associated with gastroesophageal reflux disease and is not contraindicated in these patients.

Influence of specific signal peptide mutations on the expression and secretion of the alpha-amylase inhibitor tendamistat in Streptomyces lividans.

The Streptomyces alpha-amylase inhibitor tendamistat is secreted by a signal peptide with an amino-terminal charge of +3. To elucidate the influence of the charged residues on protein secretion in Streptomyces, the amino-terminal charge was varied from +6 to neutral net charge. The effects of charge variation were analyzed in combination with three Streptomyces promoters and two transcriptional terminators. Introduction of additional positive charges significantly decreased the amount of secreted tendamistat. On the contrary, a charge reduction to +2 resulted in the doubling of inhibitor production. After exclusion of transcriptional effects, the observed alterations of inhibitor secretion by the mutants with a charge of +6 to +2 were attributed to a modulation of precursor synthesis. Furthermore, a tight coupling of synthesis and export was stated. Charge reduction to +1 or neutral charge generally reduced the yield of secreted tendamistat, yet remarkable differences were found for mutants with identical net charge. Elimination of the positive charge at a defined position resulted in the release of tendamistat precursor protein, which suggested a specific uncoupling of synthesis and translocation.

Effect of metoprolol on myocardial function and energetics in patients with nonischemic dilated cardiomyopathy: a randomized, double-blind, placebo-controlled study.

OBJECTIVES: This study examined the effects of metoprolol on left ventricular performance, efficiency, neurohormonal activation and myocardial respiratory quotient in patients with dilated cardiomyopathy. BACKGROUND: The mechanism by which beta-adrenergic blockade improves ejection fraction in patients with dilated cardiomyopathy remains an enigma. Thus, we undertook an extensive hemodynamic evaluation of this mechanism. In addition, because animal models have shown that catecholamine exposure may increase relative fatty acid utilization, we hypothesized that antagonism of sympathetic stimulation may result in increased carbohydrate utilization. METHODS: This was a randomized, double-blind, prospective trial in which 24 men with nonischemic dilated cardiomyopathy underwent cardiac catheterization before and after 3 months of therapy with metoprolol (n = 15) or placebo (n = 9) in addition to standard therapy. Pressure-volume relations were examined using a micromanometer catheter and digital ventriculography. RESULTS: At baseline, the placebo-treated patients had somewhat more advanced left ventricular dysfunction. Ejection fraction and left ventricular performance improved only in the metoprolol-treated patients. Stroke and minute work increased without an increase in myocardial oxygen consumption, suggesting increased myocardial efficiency. Further increases in ejection fraction were seen between 3 and 6 months in the metoprolol group. The placebo group had a significant increase in ejection fraction only after crossover to metoprolol. A significant relation between the change in coronary sinus norepinephrine and myocardial respiratory quotient was seen, suggesting a possible effect of adrenergic deactivation on substrate utilization. CONCLUSIONS: These data demonstrate that in patients with cardiomyopathy, metoprolol treatment improves myocardial performance and energetics, and favorably alters substrate utilization. Beta-adrenergic blocking agents, such as metoprolol, are hemodynamically and energetically beneficial in the treatment of myocardial failure.

Innovations in the struggle for self-reliance: the Hmong experience in the United States.

PIP: Theory suggests that the process by which traditional societies become more self-reliant involves entrepreneurship in experimenting with different ways to move from known to unknown forms of economic activity. Innovative projects in the US indicate that Hmong refugees are in the midst of such a movement. Progress to date has been slow and difficult, but the very fact that the projects exist and that participants in many of them are learning how to improve performance provides a basis for cautious optimism about self-reliance outcomes. The projects exist, which demonstrates motivation and willingness to work hard. Almost without exception, Hmong and American project designers launched themselves into undertakings that were new to them. The difficulties which projects encountered were far less important than the varied processes by which individuals learned from errors so that they did not repeat them. Many projects failed and disappeared, others survived in stagnant form, a few did better but were still too young to warrant ascriptions of success, and a handful did surprisingly well; this is the norm in any entrepreneurial activity. Many participants became aware of their knowledge limitations and were making efforts to overcome them. An increasing proportion of projects, especially the newer ones, were orienting themselves to providing occupational training and experience to prepare refugees for wage employment. Hmong and Americans cannot predict the eventual outcomes but can find optimism in the fact that the refugees are following in the same path as their predecessors.^ieng

Development assistance: ruined hopes and great expectations in Africa.

PIP: This paper highlights the difficulties and complexities of development assistance projects through an analysis of 2 Urban Functions in Rural Development projects conducted by the US Agency for International Development (AID) in Upper Volta and northern Cameroon in 1977-82. The general objectives of the Upper Volta project were to carry out urban function studies, develop a plan for strengthening the contributions of urban centers to rural development, develop a list of investment priorities for facilities and services, and increase the capacities of the Ministry in planning processes and methods. The 2-year project was hindered by a 1-year delay in initiating assistance due to difficulties in locating a contractor. In addition, the contractor and other team members felt there was little justification for studies of spatial organization in a country with so much evident need; rather, they focused on a small rural works program and establishment of effective local government, producing an inconsistency between team activities and the original project agreement. A request by the team to extend the project 1 year beyond its official completion date to compensate for early delays was rejected by USAID. Nonetheless, there was agreement that the project had a small positive impact in Upper Volta. Key lessons from Upper Volta were transferred to the Cameroon project. Although this project was judged to have achieved its objective of preparing a regional plan and of identifying programs for facilities, services, and small-scale enterprises, it was beset by problems of inexperience and technical underqualification of team members, poor communication, inconsistency of USAID guidelines, and methodological confusion. It is suggested that a central challenge for such programs is to create a body of qualified Americans who can work with their local counterparts in meeting the challenges of development. A measure of the success or failure of these projects should be the degree to which learning contributes to improved performance.^ieng

Transport of amino acids in renal brush border membrane vesicles. Uptake of the neutral amino acid L-alanine.

The transport of L-alanine was studied using membrane vesicles derived from the brush borders of the rabbit renal proximal tubule. Preincubation of the renal membranes with L-alanine, but not D-alanine, accelerated exchange diffusion of L-alanine, i.e. stereospecific counter transport. The equilibrium uptake of L-alanine decreased with increasing medium osmolarity. Extrapolation to infinite medium osmolarity, i.e. zero intravesicular space, indicates no uptake. These findings demonstrate that the uptake of L-alanine represents transport into membrane vesicles and not surface binding to the membrane. The presence of a Na+ gradient between the external incubation medium and the intravesicular medium stimulated L-alanine uptake. Accumulation of the amino acid in the vesicles was maximal at 5 min and then decreased, indicating efflux. The final level of uptake in the presence of the Na+ gradient was identical with that obtained in the absence of the gradient, suggesting that equilibrium was established. At the peak of the "overshoot" the uptake of L-alanine was slmost twice the final equilibrium value. These results suggest that the imposition of a large extravesicular to intravesicular gradient of Na+ effects the transient movement of L-alanine into renal brush border membrane vesicles against its concentration gradient. Stimulation of L-alanine uptake was specific for Na+. When the intravesicular medium contained no Na+, the rate of uptake enhanced with increases in the concentration of Na+ in the external medium. Increasing the Na+ gradient lowered the apparent Km for L-alanine. In the absence of the Na+ gradient, the rates of uptake of L- and D-alanine were identical. In the presence of the Na+ gradient, the rate of D-alanine uptake was stimulated, but significantly less than that of L-alanine. The uptake of L-alanine, at a given concentration of amino acid reflected the sum of the contributions from Na+ gradient-dependent and -independent transport systems. The dependent system was saturated at about 2 mM L-alanine. The independent system exhibited minimal saturability and may itself represent the sum of passive diffusion and a "carrier"-mediated system. At physiological concentrations of L-alanine, the rate of the Na+ gradient-dependent uptake was 5-fold that in the absence of the gradient. Valinomycin enhanced the Na+ gradient-dependent uptake of L-alanine, provided a K+ gradient (vesicle greater than medium) was present. This finding indicates that the Na+ gradient-dependent transport of L-alanine into renal brush border membrane vesicles is an electrogenic process and suggests that the membrane potential is a determinant of L-alanine transport. In the presence of a Na+ gradient, the uptake of L-alanine was strongly inhibited by other neutral L-amino-acids. Imino acids and glycine also inhibited, but acidic and basic amino acids were without effect. In the absence of a Na+ gradient, little selective competition was found...