Valorisation des résidus industriels de pêches pour la transformation de chitosane par technique hydrothermo-chimique

Le chitosane est une substance biodégradable d’origine naturelle obtenue par la désacétylation de la chitine, qui se trouve dans l’exosquelette des crustacés. Une de leurs applications plus récentes est le traitement des eaux. Pour favoriser l’utilisation du chitosane des exosquelettes de crustacés (crevettes, crabes, etc.) dans le traitement des eaux usées, les procédés de transformation du chitosane ont été simplifiés et optimisés. Dans la présente étude, les crustacés de crevette grise (Palaemodiae) ont été utilisés pour extraire le chitosane. Les expériences ont porté sur les effets des interactions de la concentration de la solution alcaline, du temps et de la température de réaction sur le degré de désacétylation. En plus de simplifier le processus de transformation de trois à deux étapes, les résultats montrent l’influence de la concentration d’hydroxyde de sodium (7,5‑ 12,5 M), du temps de réaction (30 ‑ 180 min) et de la température (80 ‑ 120 oC) sur le degré de désacétylation. La méthode de la spectroscopie infrarouge en film mince a été utilisée pour analyser le degré de désacétylation du chitosane. Un degré de désacétylation de 90 % a été atteint avec une concentration de la solution alcaline de 12,5 M, un temps de réaction de 120 min et une température de 110 oC. Par ailleurs, en réduisant le nombre d’étapes de transformation et la consommation de réactifs, le procédé développé est plus économique et a une meilleure performance environnementale.Chitosan is a natural biodegradable biopolymer produced from chitin, a polysaccharide derived from the shells of shrimp, crab and lobster. The development of commercial applications of chitin and chitosan in different fields such as biomedicine, nutrition, food processing, agriculture, cosmetics, and wastewater treatment has rapidly expanded in recent years. This paper investigates the hydrothermal production of chitosan from the carapace of gray shrimp (Palaemodiae) for use as a coagulant in wastewater treatment.To obtain chitosan from shrimp exoskeletons, they were treated following two different steps. The first step was the demineralization of the shrimp’s exoskeleton, where calcium was removed using dilute HCl. The second deacetylation step completely dissolved the shrimp exoskeleton using a NaOH solution. In both steps, the ratio between solution digestive and exoskeleton was studied (1:10 (w:v)). For the demineralization process, the concentration of HCl was varied from 0.5 to 3.5 M in 0.5 M intervals at constant temperatures of 25oC and 50oC. The comparison of the results using these two temperatures indicated that the most favourable demineralization occurred after 6 h at 25oC and after 2 h at 50oC at a HCl concentration of 2 M. In this case, it was not necessary to use a HCl concentration greater than 2 M due to the fixed reaction time. When the HCl solution was heated, the reaction time of the demineralization process was reduced by a factor of three compared to that when room temperature HCl was used under the same conditions. Moreover, this reaction followed a pseudo-second-order equation with approximate rate constant of 2.38 L g‑1 min‑1 at 25oC in 1.5 M HCl.The effectiveness of the transformation to chitosan depends on the interaction among the sodium hydroxide concentration, the reaction time and the temperature at which the deacetylation process occurs. The influence of the concentration of the alkaline solution, the reaction temperature, and the reaction time on the degree of deacetylation (DD) was investigated. The DD obtained was quantitatively analyzed by thin film infrared spectroscopy (IR). Film thickness was measured by using a micrometer with the smallest possible unit measurement count of 0.01 mm. First, exoskeletons were exposed to NaOH concentrations of 7.5 M, 10 M and 12.5 M for 60 min at various temperatures ranging from 60oC to 120oC at intervals of 20oC. Second, the reaction time was changed from 30 to 180 min at 100oC at 30 min intervals using the same NaOH concentrations previously mentioned. The results show that the factors that influence the DD values were the reaction temperature and the concentration of NaOH. However, based on these experiments, the concentration of NaOH influences the DD values the most. The DD values of chitosan production began to reach a constant level when the reaction temperature was greater than 100oC. As a result, after one hour at 110oC, chitosan production was obtained with different DD values of 60%, 67%, and 78% at NaOH concentrations of 10 M, 11.25 M and 12.5 M respectively. Nevertheless, chitosan could not be formed at 7.5 M NaOH, even though the reaction time was 3 h. Furthermore, when the reaction time was longer than 120 min, the DD values of chitosan increased slowly.Therefore, the optimum conditions required for the deacetylation production of chitosan from gray shrimp carapace (DD of 90%), to be applied in wastewater treatment, are as follows: the exoskeleton should be exposed to a solution of 12.5 M NaOH (45%) for 2 h at 110oC. This product is generally termed chitosan when it has greater than 65% of the acetylic groups removed.By diminishing the number of steps and reducing the chemical reagents needed, this study demonstrates the economical and environmental advantages of using chitosan as a coagulant to treat wastewater

From Understanding Cellular Function to Novel Drug Discovery: The Role of Planar Patch-Clamp Array Chip Technology

All excitable cell functions rely upon ion channels that are embedded in their plasma membrane. Perturbations of ion channel structure or function result in pathologies ranging from cardiac dysfunction to neurodegenerative disorders. Consequently, to understand the functions of excitable cells and to remedy their pathophysiology, it is important to understand the ion channel functions under various experimental conditions – including exposure to novel drug targets. Glass pipette patch-clamp is the state of the art technique to monitor the intrinsic and synaptic properties of neurons. However, this technique is labor intensive and has low data throughput. Planar patch-clamp chips, integrated into automated systems, offer high throughputs but are limited to isolated cells from suspensions, thus limiting their use in modeling physiological function. These chips are therefore not most suitable for studies involving neuronal communication. Multielectrode arrays (MEAs), in contrast, have the ability to monitor network activity by measuring local field potentials from multiple extracellular sites, but specific ion channel activity is challenging to extract from these multiplexed signals. Here we describe a novel planar patch-clamp chip technology that enables the simultaneous high-resolution electrophysiological interrogation of individual neurons at multiple sites in synaptically connected neuronal networks, thereby combining the advantages of MEA and patch-clamp techniques. Each neuron can be probed through an aperture that connects to a dedicated subterranean microfluidic channel. Neurons growing in networks are aligned to the apertures by physisorbed or chemisorbed chemical cues. In this review, we describe the design and fabrication process of these chips, approaches to chemical patterning for cell placement, and present physiological data from cultured neuronal cells

Alkaline phosphatase variation during carfilzomib treatment is associated with best response in multiple myeloma patients

The ubiquitin–proteasome pathway regulates bone formation through osteoblast differentiation. We analyzed variation alkaline phosphatase (ALP) during carfilzomib treatment. Data from 38 patients enrolled in the PX‐171‐003 and 29 patients in PX‐171‐004 studies, for patients with relapsed/refractory myeloma, were analyzed. All patients received 20 mg/m 2 of carfilzomib on Days 1, 2, 8, 9, 15, and 16 of a 28‐day cycle. Sixty‐seven patients from ALP data were evaluable. In PX‐171‐003, the ORR (>PR) was 18% and the clinical benefit response (CBR; >MR) was 26%, while in PX‐171‐004, the ORR was 35.5% overall and 57% in bortezomib‐naive patients. ALP increment from baseline was statistically different in patients who achieved ≥VGPR compared with all others on Days 1 ( P  = 0.0049) and 8 ( P  = 0.006) of Cycle 2. In patients achieving a VGPR or better, ALP increased more than 15 units per liter at Cycle 2 Day 1 over baseline. An ALP increase over the same period of time was seen in 26%, 13% and 11% of patients achieving PR, MR, and SD, respectively. This retrospective analysis of patients with relapsed or refractory myeloma treated with single‐agent carfilzomib indicates that early elevation in ALP is associated with subsequent myeloma response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86807/1/j.1600-0609.2011.01602.x.pd

Synaptic Neurotransmission Depression in Ventral Tegmental Dopamine Neurons and Cannabinoid-Associated Addictive Learning

Drug addiction is an association of compulsive drug use with long-term associative learning/memory. Multiple forms of learning/memory are primarily subserved by activity- or experience-dependent synaptic long-term potentiation (LTP) and long-term depression (LTD). Recent studies suggest LTP expression in locally activated glutamate synapses onto dopamine neurons (local Glu-DA synapses) of the midbrain ventral tegmental area (VTA) following a single or chronic exposure to many drugs of abuse, whereas a single exposure to cannabinoid did not significantly affect synaptic plasticity at these synapses. It is unknown whether chronic exposure of cannabis (marijuana or cannabinoids), the most commonly used illicit drug worldwide, induce LTP or LTD at these synapses. More importantly, whether such alterations in VTA synaptic plasticity causatively contribute to drug addictive behavior has not previously been addressed. Here we show in rats that chronic cannabinoid exposure activates VTA cannabinoid CB1 receptors to induce transient neurotransmission depression at VTA local Glu-DA synapses through activation of NMDA receptors and subsequent endocytosis of AMPA receptor GluR2 subunits. A GluR2-derived peptide blocks cannabinoid-induced VTA synaptic depression and conditioned place preference, i.e., learning to associate drug exposure with environmental cues. These data not only provide the first evidence, to our knowledge, that NMDA receptor-dependent synaptic depression at VTA dopamine circuitry requires GluR2 endocytosis, but also suggest an essential contribution of such synaptic depression to cannabinoid-associated addictive learning, in addition to pointing to novel pharmacological strategies for the treatment of cannabis addiction

Traitement des eaux usées par coagulation-floculation avec recirculation des boues chimiques : influence des réactifs

Three series of tests were carried out at laboratory and pilot levels to examine the functions of reagents (coagulant, flocculant, sludge) involved in a coagulation-flocculation process with chemical sludge recycling. Results showed that the recycled sludge participates favourably in the process. The gains in efficiency are particularely significant for lower coagulant concentrations when flocculant concentration is not limitative. The pollutant removal increases with the sludge recycling load but seems reversible and dependent on coagulant concentration. Results also revealed the advantages of recycling sludge before injecting coagulant. To decrease the total chemical costs at a wastewater treatment plant, the strategy must focus on diminishing the coagulant concentration and increasing the flocculant concentration while maintaining a sufficient recycling sludge load to ensure gains in efficiency.Key words: recycling, sludge, preformed flocs, reagents, coagulation-flocculation, treatment, wastewater. </jats:p