Transfer and degradation of polyacrylamide-based flocculants in hydrosystems: a review.

The aim of this review was to summarize information and scientific data from the literature dedicated to the fate of polyacrylamide (PAM)-based flocculants in hydrosystems. Flocculants, usually composed of PAMs, are widely used in several industrial fields, particularly in minerals extraction, to enhance solid/liquid separation in water containing suspended matter. These polymers can contain residual monomer of acrylamide (AMD), which is known to be a toxic compound. This review focuses on the mechanisms of transfer and degradation, which can affect both PAM and residual AMD, with a special attention given to the potential release of AMD during PAM degradation. Due to the ability of PAM to adsorb onto mineral particles, its transport in surface water, groundwater, and soils is rather limited and restricted to specific conditions. PAM can also be a subject of biodegradation, photodegradation, and mechanical degradation, but most of the studies report slow degradation rates without AMD release. On the contrary, the adsorption of AMD onto particles is very low, which could favor its transfer in surface waters and groundwater. However, AMD transfer is likely to be limited by quick microbial degradation.

Microbial aerobic and anaerobic degradation of acrylamide in sludge and water under environmental conditions--case study in a sand and gravel quarry.

Polyacrylamides (PAMs) are used in sand and gravel quarries as water purification flocculants for recycling process water in a recycling loop system where the flocculants remove fine particles in the form of sludge. The PAM-based flocculants, however, contain residual amounts of acrylamide (AMD) that did not react during the polymerization process. This acrylamide is released into the environment when the sludge is discharged into a settling basin. Here, we explore the microbial diversity and the potential for AMD biodegradation in water and sludge samples collected in a quarry site submitted to low AMD concentrations. The microbial diversity, analyzed by culture-dependent methods and the denaturing gradient gel electrophoresis approach, reveals the presence of Proteobacteria, Cyanobacteria, and Actinobacteria, among which some species are known to have an AMD biodegradation activity. Results also show that the two main parts of the water recycling loop-the washing process and the settling basin-display significantly different bacterial profiles. The exposure time with residual AMD could, thus, be one of the parameters that lead to a selection of specific bacterial species. AMD degradation experiments with 0.5 g L(-1) AMD showed a high potential for biodegradation in all parts of the washing process, except the make-up water. The AMD biodegradation potential in samples collected from the washing process and settling basin was also analyzed taking into account on-site conditions: low (12 °C) and high (25 °C) temperatures reflecting the winter and summer seasons, and AMD concentrations of 50 µg L(-1). Batch tests showed rapid (as little as 18 h) AMD biodegradation under aerobic and anaerobic conditions at both the winter and summer temperatures, although there was a greater lag time before activity started with the AMD biodegradation at 12 °C. This study, thus, demonstrates that bacteria present in sludge and water samples exert an in situ and rapid biodegradation of AMD at low concentration, whatever the season, and in both the aerobic and anaerobic parts of the water recycling system.

An optimized method for intensive screening of molecules that stimulate beta-defensin 2 or 3 (hBD2 or hBD3) expression in cultured normal human keratinocytes.

Normal human skin controls the intrusion of microorganisms by the production of peptide antibiotics such as defensins. The aim of our study was to develop a culture model of normal human keratinocytes for optimal beta-defensin mRNA detection which allows the screening of molecules able to stimulate hBD2 and hBD3 without inducing pro-inflammatory cytokines. A keratinocyte culture model in 96-well plates, in high calcium medium (1.7 mm) allowed to analyze hBD2 and hBD3 mRNA expression in basal condition and after cell stimulation by products from diverse vegetal extracts. The release of IL-8 and the chemokine MIP-3alpha was also evaluated in cell supernatants by ELISA. Among the 184 extracts tested, 75 showed a stimulatory effect on beta-defensin expression: 40 on hBD2, 26 on hBD3 and nine on both defensins. Fifteen of these substances which also induced the release of pro-inflammatory cytokines were eliminated. Among the other substances, four were selected and were analyzed in a dose-dependent study (n = 4) by real-time quantitative RT-PCR and completed by a measure of MIP-3alpha, IL-8 and IL-1alpha levels. These data underline the important necessity of screening result controls by a quantitative method reproduced at least three times. This new method of intensive screening allowed us to exhibit vegetal extracts that were able to stimulate epidermal beta-defensin expression without inducing an up-secretion of pro-inflammatory cytokines.

In vitro stimulation of synthesis of key DEJ constituents in a reconstructed skin model: a quantitative study.

Fighting skin ageing is one of the major targets of cosmetology research. However, traditional approaches to skin ageing using stimulation of basal keratinocyte proliferation and fibroblastic neosynthesis appear today to be incomplete, particularly considering changes occurring at the dermal-epidermal junction (DEJ) during the course of ageing. Unfortunately, the lack of in vitro model limits the exploration process of the phenomena of DEJ ageing, and particularly the evaluation of the changes of key components, that are laminin-5, types IV and VII collagens. The aim of this work was to provide an in vitro model of reconstructed skin, base for new dosage and identification methods for qualitative and quantitative analysis of the key components of DEJ. Reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative RT-PCR were successfully applied to this model to analyse mRNA of laminin-5, types IV and VII collagens and their variation in 'young' and 'mature' reconstructed skin model. Finally, this model was used to test the activity of ingredients for cosmetic application, in order to modulate the expression of the major components of DEJ. To conclude, we demonstrated that this in vitro model of reconstructed young and mature skin provides a useful tool to get into the biology of the DEJ, key structure of the skin, and specifically into its dynamic changes during the ageing process.

Calcium triggers beta-defensin (hBD-2 and hBD-3) and chemokine macrophage inflammatory protein-3 alpha (MIP-3alpha/CCL20) expression in monolayers of activated human keratinocytes.

The inducible epidermal beta-defensins and the chemokine macrophage inflammatory protein-3alpha (MIP-3alpha/CCL20) are important mediators involved in innate and adaptive immunity and in the recruitment of immune cells. The aim of our study was to determine whether calcium could trigger the induction of beta-defensins (hBD-2 and hBD-3) mRNA and the release of MIP-3alpha by normal human keratinocyte monolayers. Epidermal cells derived from foreskin were cultured in defined medium supplemented with different calcium levels (0.09, 0.8 and 1.7 mM) and were stimulated or not with the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha 1-500 ng/ml) or interferon-gamma (INF-gamma 1-100 ng/ml). A high calcium concentration (1.7 mM) alone applied in culture medium for 4 days was sufficient to induce hBD-2 and hBD-3 mRNA expression. Whatever interindividual variability in the expression of hBD-2 and hBD-3 mRNA and MIP-3alpha secretion, the addition of TNF-alpha for a short duration (26h), initiated a dose-dependent and coordinated up-regulation of hBD-2 and hBD-3 mRNA and MIP-3alpha release in keratinocyte cultures. Unlike hBD-2 and hBD-3 mRNA was preferentially stimulated by IFN-gamma rather than TNF-alpha. In our experimental conditions, L-isoleucine, described to stimulate beta-defensin in bovine epithelial cells, did not exert any effect either on hBD-2 and hBD-3 transcripts or MIP-3alpha protein. Taken together, these results confirm the major role of the maturation/differentiation process of normal human keratinocytes in the induction of inducible beta-defensins and MIP-3alpha chemokine, which contribute in vivo to the immunosurveillance of the skin barrier function.

The effect of drugs and lead maturation on atrial electrograms during sinus rhythm and atrial fibrillation.

Antitachycardia devices need more accurate means to identify arrhythmias. Previous studies have found that sinus rhythm can be distinguished from a variety of tachyarrhythmias by algorithms that are based on time-domain and frequency-domain analysis of intracardiac electrograms. Amplitude distribution analysis (time-domain) and power density spectral analysis (frequency-domain) are two of the techniques that have seemed to hold promise. However, previous studies have not evaluated whether lead maturation or drugs such as lidocaine, propranolol, verapamil, or isoproterenol can interfere with the ability of these algorithms to distinguish among cardiac rhythms. In the present study, five dogs had permanent atrial pacing leads placed. On a series of days, recordings were made from the atrial leads during sinus rhythm and induced sustained atrial fibrillation, both before and after administration of cardioactive drugs. For up to 1 month after implantation, progressive lead maturation did not prevent differentiation of atrial fibrillation from sinus rhythm by either amplitude distribution analysis or power density spectral analysis. However, the difference between the power density spectra of sinus rhythm and atrial fibrillation became progressively less with time. Isoproterenol, lidocaine, verapamil, and propranolol had no consistent effects on amplitude distribution analysis of atrial electrograms during sinus rhythm or atrial fibrillation. However, there were marked effects of drugs on amplitude distribution characteristics in individual dogs. Propranolol and lidocaine produced consistent changes in power density spectra during sinus rhythm and atrial fibrillation, respectively; both drugs reduced the ability of power density spectral analysis to differentiate sinus rhythm from atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of atrial fibrillation using electrograms from chronic leads: evaluation of computer algorithms.

This study compares the performance of three detection algorithms for the recognition of atrial fibrillation in chronic pacing leads. Multiple serial recordings were obtained of wideband and filtered electrograms from chronic atrial and ventricular leads in dogs for a period up to 55 days following implantation. Each dog was recorded in sinus rhythm and induced atrial fibrillation. Four days were chosen for processing: The day of implantation and a day in the first, second or third, and fifth weeks. Three signal processing methods were assessed for performance in detection of atrial fibrillation: software recognition of rate with automatic threshold control, amplitude distribution, and frequency spectral analysis. A software trigger for rate determination was adjusted to thresholds of 10, 20, and 30% of maximum baseline-to-peak amplitude. At 10%, a rate boundary anywhere between 420 and 560 beats per minute (bpm) perfectly separated atrial fibrillation from sinus rhythm even though atrial electrograms were contaminated with large QRS deflections and double-sensing was present. At 20% and 30%, a rate boundary around 300 bpm could be used, but sensitivity and specificity were reduced to 90%. In amplitude distribution analysis, a percent of time within a baseline window provided perfect separation of atrial fibrillation from sinus rhythm. In all cases, the signal was within this window less than 43% of the time in atrial fibrillation, and more than 43% in sinus rhythm. In spectral analysis, frequency bands were examined for power content. In the 6 to 30 Hz band atrial fibrillation contained the greater power. Choosing 58% of total power as a discriminant, sensitivity and specificity of atrial fibrillation detection were 100% and 95% respectively.