Rheology of human faeces and pathophysiology of defaecation.

BACKGROUND: Rectal evacuation involves multiple mechanisms that are not completely understood. The aim of this study was to quantify the rheologic property, i.e., yield stress, which governs the ease of deformation of a range of faeces of differing consistency and understand its influence on the pathophysiology of defaecation. METHODS: Yield stresses of faeces of differing consistencies and Bristol scores were determined by the Vane test. We then explored the effects of this property on ease of defecation using a simple static model of the recto-anal junction based on the laws of flow for yield stress pastes and checked the conclusions by X-ray defaecography experience. RESULTS: The yield stress of faeces increased exponentially with their solid content, from 20 to 8000 Pa. The static model of the recto-anal junction showed that evacuation of faeces of normal consistency and yield stress is possible with moderate dilatation of the anal canal, whilst the evacuation of faeces with higher yield stress requires greater dilatation of the anal canal. X-ray defaecography showed that such increases occurred in vivo. CONCLUSIONS: The diameter of the recto-anal junction is increased to enable the passage of feces with high yield stress. The finite limits to such dilation likely contribute to fecal impaction. Hence, difficulties in defaecation may result either from unduly high yield stress or pathologies of reflex recto-anal dilatation or a combination of the two.

European survey on national training activities in clinical research.

BACKGROUND: Investigator-initiated clinical studies (IITs) are crucial to generate reliable evidence that answers questions of day-to-day clinical practice. Many challenges make IITs a complex endeavour, for example, IITs often need to be multinational in order to recruit a sufficient number of patients. Recent studies highlighted that well-trained study personnel are a major factor to conduct such complex IITs successfully. As of today, however, no overview of the European training activities, requirements and career options for clinical study personnel exists. METHODS: To fill this knowledge gap, a survey was performed in all 11 member and observer countries of the European Clinical Research Infrastructure Network (ECRIN), using a standardised questionnaire. Three rounds of data collection were performed to maximize completeness and comparability of the received answers. The survey aimed to describe the landscape of academic training opportunities, to facilitate the exchange of expertise and experience among countries and to identify new fields of action. RESULTS: The survey found that training for Good Clinical Practice (GCP) and investigator training is offered in all but one country. A specific training for study nurses or study coordinators is also either provided or planned in ten out of eleven countries. A majority of countries train in monitoring and clinical pharmacovigilance and offer specific training for principal investigators but only few countries also train operators of clinical research organisations (CRO) or provide training for methodology and quality management systems (QMS). Minimal requirements for study-specific functions cover GCP in ten countries. Only three countries issued no requirements or recommendations regarding the continuous training of study personnel. Yet, only four countries developed a national strategy for training in clinical research and the career options for clinical researchers are still limited in the majority of countries. CONCLUSIONS: There is a substantial and impressive investment in training and education of clinical research in the individual ECRIN countries. But so far, a systematic approach for (top-down) strategic and overarching considerations and cross-network exchange is missing. Exchange of available curricula and sets of core competencies between countries could be a starting point for improving the situation.

Does water availability regulate biomass partitioning between trunk and branches?

The extent to which a vertical trunk is differentiated from its branches is a key trait for the architecture of trees and may affect interspecific relationships. In this study, we analysed the effect of soil water availability on biomass partitioning for Nothofagus pumilio by means of a nursery experiment. Juvenile trees were subject to three irrigation conditions: no irrigation, intermediate irrigation and high irrigation. Irrigation conditions emulated the mean precipitation of the most representative environments inhabited by N. pumilio. Changes in soil water availability modified the biomass partitioning patterns of trees. In comparison to the other two conditions, high irrigation caused: (i) a higher ratio of biomass partitioning to stems than roots; (ii) more trunk growth in relation to its branches; and (iii) more photosynthetic organs relative to the aboveground biomass. Trunk size relative to that of its most recent branches was not increased by water availability. Water availability may play a significant role in the capacity of N. pumilio for space occupation due to the effects on axis differentiation.

A new way to apply ultrasound in cross-flow ultrafiltration: application to colloidal suspensions.

A new coupling of ultrasound device with membrane process has been developed in order to enhance cross-flow ultrafiltration of colloidal suspensions usually involved in several industrial applications included bio and agro industries, water and sludge treatment. In order to reduce mass transfer resistances induced by fouling and concentration polarization, which both are main limitations in membrane separation process continuous ultrasound is applied with the help of a vibrating blade (20 kHz) located in the feed channel all over the membrane surface (8mm between membrane surface and the blade). Hydrodynamic aspects were also taking into account by the control of the rectangular geometry of the feed channel. Three colloidal suspensions with different kinds of colloidal interaction (attractive, repulsive) were chosen to evaluate the effect of their physico-chemical properties on the filtration. For a 90 W power (20.5 W cm(-2)) and a continuous flow rate, permeation fluxes are increased for each studied colloidal suspension, without damaging the membrane. The results show that the flux increase depends on the initial structural properties of filtered dispersion in terms of colloidal interaction and spatial organizations. For instance, a Montmorillonite Wyoming-Na clay suspension was filtered at 1.5 × 10(5)Pa transmembrane pressure. Its permeation flux is increased by a factor 7.1, from 13.6 L m(-2)h(-1) without ultrasound to 97 L m(-2)h(-1) with ultrasound.

In situ characterization by SAXS of concentration polarization layers during cross-flow ultrafiltration of Laponite dispersions.

The structural organization inside the concentration polarization layer during cross-flow membrane separation process of Laponite colloidal dispersions has been characterized for the first time by in situ time-resolved small-angle X-ray scattering (SAXS). Thanks to the development of new "SAXS cross-flow filtration cells", concentration profiles have been measured as a function of the distance z from the membrane surface with 50 µm accuracy and linked to the permeation flux, cross-flow, and transmembrane pressure registered simultaneously. Different rheological behaviors (thixotropic gel with a yield stress or shear thinning sol) have been explored by controlling the mutual interactions between the particles as a result on the addition of peptizer. The structural reversibility of the concentration polarization layer has been demonstrated being in agreement with permeation flux measurements. These observations were related to structure of the dispersions under flow and their osmotic pressure.

Alumina interaction with AMPS-MPEG copolymers produced by RAFT polymerization: stability and rheological behavior.

Different copolymers of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS), methoxypolyethyleneglycol methacrylate (MPEG), were prepared using two methods of radical polymerization: classical and RAFT-controlled radical polymerization. The effect of polymer structure and architecture on the adsorption behavior, electrokinetic and rheological properties of the alumina suspensions was investigated. Adsorption isotherms showed that copolymer interaction depended not only on the ratio of the monomers and their distribution within the macromolecular backbone, but also on the method of copolymerization. Electrokinetic analysis indicated that adsorption of the copolymer is accompanied by a shift in the isoelectric point (IEP) towards acid pH values. Above a certain concentration, of the order of 1 wt%, the absolute value of the zeta-potential reaches a saturation plateau. At this stage, the maximum zeta-potential value (in absolute value) depends on both the ratio of the monomers for statistical copolymer and the length of the two blocks in the case of block distribution. The rheological behavior is greatly affected in the presence of added polymer; the viscosity of the alumina suspension decreases and reaches an optimum, which depends on both the ratio of the monomers and their distribution within the macromolecular backbone. The viscoelastic properties of the suspensions were found to be functions of both the structure and the architecture of the copolymer. Adding AMPS-MPEG copolymer increases the stability of the suspension via electrostatic effects, but also via steric effects induced by the polyethylene glycol (PEG) segments. The steric contribution to the stabilization process is much important in the presence of block distribution, which is more efficient as dispersant for concentrated alumina suspensions.

Spatial and temporal in situ evolution of the concentration profile during casein micelle ultrafiltration probed by small-angle X-ray scattering.

Understanding the mechanisms involved in structural development in the vicinity of membrane constitutes a considerable challenge in the improvement of ultrafiltration process in industrial applications. In situ small-angle X-ray scattering (SAXS) performed with custom-made ultrafiltration cell has permitted the structural arrangement to be probed and concentration profiles to be obtained in deposited layers during frontal filtration of casein micelle suspension. SAXS allowed the structure of the accumulated layers of casein micelles between 280 microm and 1 mm from the membrane surface to be followed at length scales from a few nanometers to about 100 nm. These results have been combined with hydrodynamic measurements (permeation flux) and rheological investigations. Under frontal filtration, the time dependence of concentration at different distances from the membrane surface has been obtained. This temporal evolution is marked by an exponential increase of the concentration followed by a slower growth which has been associated with a change in the rheological behavior of the suspension from Newtonian to shear thinning behavior.

Dispersion of alumina suspension using comb-like and diblock copolymers produced by RAFT polymerization of AMPS and MPEG.

Different copolymers of 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS) methoxypolyethyleneglycol methacrylate (MPEG) with statistical and diblock distributions were prepared using RAFT-controlled radical polymerization. The effect of polymer architecture and monomer ratio on the adsorption behavior, electrokinetic, and stability properties of the alumina suspensions was investigated. Adsorption isotherms showed that copolymer interaction depended on both the ratio of the monomers and their distribution within the macromolecular backbone. Changes in the electrokinetic properties of the alumina suspension after addition of the copolymers were investigated by monitoring the particle zeta-potential as a function of pH. A continuous shift in the isoelectric point IEP to a more acidic value was observed and particle charges were reversed when the amount of copolymer added exceeded a critical level.

Alumina interaction with AMPS-MPEG random copolymers III. Effect of PEG segment length on adsorption, electrokinetic and rheological behavior.

The effect of different 2-acrylamido-2-methylpropanesulfonic acid sodium salt (AMPS)-methoxypolyethyleneglycol methacrylate (MPEG) comb-like copolymers on the adsorption behavior, electrokinetic and rheological properties of alumina suspensions has been investigated. The change in adsorption isotherms with the content of the two monomers, the medium pH and the ionic strength indicated that the interaction of these copolymers was found to be controlled by both the fraction of ionic groups on the polymer and by the length of the polyethyleneglycol (PEG) segments. Adsorption of the copolymers on alumina particles is accompanied by a shift in the IEP toward acid pH values and may lead to a charge reversal above a certain level. The presence of the PEG segment equally affects the magnitude of the zeta potential by moving the shear plane forward. Addition of the copolymers greatly affects the rheological behavior of the suspension; the viscosity at a defined shear rate decreases and reaches an optimum, which is all the lower as the fraction of the ionic groups is higher. The dispersing effect of the copolymer was controlled by both the ionization level of the copolymer and by the length of the PEG segments.

Structure and rheological behavior of casein micelle suspensions during ultrafiltration process.

The stability and mechanism underlying the formation of deposits of casein micelles during ultrafiltration process were investigated by small-angle and ultra small-angle x-ray scattering (SAXS and USAXS). The casein micelle dispersions consisted of phospho-caseinate model powders and the measurements probed length scales ranging from 1 to 2000 nm. Rheometric and frontal filtration measurements were combined with SAXS to establish the relationship between the rheological behavior of deposits (shear and/or compression) and the corresponding microstructure. The results revealed two characteristic length scales for the equilibrium structure with radius of gyrations R(g), about 100 and 5.6 nm pertaining to the globular micelles and their non-globular internal structure, respectively. The SAXS measurements further indicated that the increase of temperature from 20 to 70 degrees C or the decrease of pH from 6.6 to 6 lead to agglomeration of the globular micelles. In situ scattering measurements showed that the decrease of permeation flows is directly related to the deformation and compression of the micelles in the immediate vicinity of the membrane.

Plastic and elastic properties of the systems interstratified clay-water-electrolyte-xanthan.

The present study concerns the rheological behavior of the Jebel Shemsi clay dispersions (Shp). Shp is an interstratified illite/smectite clay from southern Tunisia. The influences of clay concentration, NaCl, and xanthan-a semirigid polymer-on the yield stress, the elastic modulus, and the xanthan adsorption were investigated. The sol-gel transition and the scale laws of rheometric properties are established. Progressive addition of NaCl to the clay dispersions decreases the thickness of the diffuse double layer, which makes the system rigid, increasing the yield and the elastic modulus. In the presence of xanthan, the negative surface charges become higher and the repulsive interparticle interactions increase; consequently the yield and the elastic modulus increase. The xanthan adsorption on the clay particle surface increases slightly with the NaCl concentration. The particle aggregation due to the salt and the particle dispersion due to the polymer are observed. The behavior of this interstratified clay is compared to that found for pure smectite. The 15% illite stratified with smectite in the Shp clay does not change the gels' rheological properties significantly. Meanwhile the amount of Shp clay needed to obtain a gel is more important than in the case of a pure smectite.

Alumina interaction with AMPS-MPEG random copolymers I. Adsorption and electrokinetic behavior.

Adsorption of brush copolymers, bearing sulfonate groups and polyethylene glycol segments, on to alumina particles in suspension in water has been investigated. Study of the adsorption isotherms revealed that the copolymers displayed a strong affinity for the surface of the alumina regardless of the fraction of ionic groups on the polymer. For poly(ethylene glycol) content greater than 50%, the adsorption isotherms revealed an initial adsorption plateau followed by a second one. The shape of the adsorption isotherms was interpreted in terms of the polymer configuration at the solid-to-liquid interface. The effects of the pH and the ionic force on adsorption were studied and connected to the effects of interaction between chain segments at the surface of the alumina particles. Changes in the electrokinetic properties of the alumina particles after addition of the copolymers were investigated by following the zeta potential of particles as a function of pH. In the presence of the copolymer continuous shift of the isoelectric point IEP to a more acidic values was observed. Beyond a certain concentration the zeta potential remained negative regardless of the pH.

Early prediction in acute pancreatitis: the contribution of amylase and lipase levels in peritoneal fluid.

CONTEXT: Predicting the severity of acute pancreatitis early in the course of the disease is still difficult. OBJECTIVE: The value of amylase and lipase levels in serum and peritoneal fluid might be of value in predicting the course of acute pancreatitis. DESIGN: Prospective study. PATIENTS: One-hundred and sixty-seven patients with acute pancreatitis as confirmed by computed tomography scan within 24 hours of admission were studied. MAIN OUTCOME MEASURES: Each patient was given an enzymatic score which reflected the predominance of serum or peritoneal levels of amylase and/or lipase. Enzymatic score was 0 if neither enzyme was predominant in the peritoneal fluid, 1 if amylase or lipase alone were predominant and 2 if both enzymes were predominant. The predictive value of the enzymatic score or computed tomography scan for a severe attack was determined. RESULTS: One-hundred and thirty-three attacks were graded as mild (79.6%) and 34 were considered as severe (20.4%). The frequency of severe acute pancreatitis significantly increased as the enzymatic score increased (5.4%, 12.5%, and 31.7% in 0, 1, and 2 enzymatic score patients, respectively; P<0.001). An enzymatic score greater than 0 predicted a severe outcome in 32 of 34 patients (sensitivity 94.1%, specificity 26.3%), whereas an enzymatic score of 2 predicted a severe attack in 26 of 34 patients (sensitivity 76.5%, specificity 57.9%). Edema on computed tomography scan was found in 97 of 129 mild attacks (specificity 75.2%) and necrosis in 25 of 33 severe attacks (sensitivity 75.8%), whereas all patients with severe attacks exhibited extrapancreatic acute fluid collection (sensitivity 100%, specificity 34.9%). CONCLUSIONS: Peritoneal dialysis is less predictive and more cumbersome than a computed tomography scan in the early prediction of acute pancreatitis.

Effect of pH on Rheological Properties of Purified Sodium Bentonite Suspensions.

The effect of pH on the rheological behavior of three purified sodium bentonite (HP, GP, and WP) suspensions is studied. Each clay is studied as a function of pH, at a chosen constant concentration. These concentrations correspond to the lower concentrations at which the yield stress can be detected. They are 12.5, 8.5, and 5.5% w/w, respectively, for the three clay suspensions. The natural pH of these samples measured by a pH meter or by a colorimetric test paper are usually neutral or weakly basic. To obtain a large range of pH values, HCl or NaOH solutions are used in the preparation of the suspensions. From the natural pH and when pH values become more basic, the yield stress measured, using the vane method, decreases. It reaches a minimum before it increases sharply, at very high basic medium. When the pH decreases, the yield stress increases and reaches a maximum for pH in weakly acidic media before decreasing again, in a very highly acidic medium where the structure of the clay is probably attacked. The pH where the maximum appears depends on the nature of the clay. At the same time, the conductivity and the electrophoretic mobility are measured, at the different pH values, on the supernatants obtained after centrifugation of the previous suspensions. The isoelectric points of the edges of the three studied purified sodium bentonites, which are of a great importance for the understanding of the interactions between the clay particles, have been determined. In summary, a correlation between rheological and electrokinetic results, is shown. And moreover, different types of interactions between clay particles are deduced, depending on the pH value of the medium. At acidic medium, there is a dominance of the attractive forces between particles. At high basic medium, interparticle interactions lead to a card-house-like structure based on edge to edge, edge to face, and face to face repulsion, instead of attraction. Copyright 1999 Academic Press.

[Antispasmodic effect of warm water administered in aerosols or parenteral injections]. / Effets antispasmodiques d'une eau thermale administrée en aérosols et en injections parentérales.

The aerosol of thermal water given just before the administration of spasmogenic substances did not prevent the histamine or acetylcholine induced bronchospasm. After a daily parenteral dose of thermal water during 21 days, a systemic delay of the bronchospasm induced by both mediators was observed. With arsenic pretreatment the delay in onset of bronchospasm was shorter.

Report of a clinical trial of a Canadian preparation of antihemophilic factor.

A clinical trial of a Canadian preparation of antihemophilic factor has been completed. The mean percentage increase in the factor VIII coagulant activity in the plasma was determined to be 2.1 +/- 0.8 per unit per kilogram dose, which compares very favourably with published data. The mean half-life of antihemophilic factor was found to be 14.7 hours. Side effects and reactions to the product were minimal and the product has been rated as clinically effective. No significant differences between lots were noted in the in vivo response or the half-life.

[Proceedings: Erythrocyte 2,3-diphosphoglycerate during the development of myocardial infarct. Concerning 118 cases]. / Le 2,3-diphosphoglycérate érythrocytaire au cours de l'évolution de l'infarctus du myocarde

In four groups of patients with myocardial infarction the increase of 2.3-DPG concentration in erythrocyte was important when complications appeared during the evolution or when the patients died.