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Proteolytic cleavage of stingray phospholipase A2: Isolation and biochemical characterization of an active N-terminal form
Abir G Ben Bacha, Hafedh Mejdoub
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-124
Abstract: The effect of some proteolytic enzymes on SPLA2 was checked. Chymotrypsin and trypsin were able to hydrolyze SPLA2 in different ways. In both cases, only N-terminal fragments were accumulated during the hydrolysis, whereas no C-terminal fragment was obtained in either case. Tryptic and chymotryptic attack generated 13 kDa and 12 kDa forms of SPLA2, respectively. Interestingly, the SPLA2 13 kDa form was inactive, whereas the SPLA2 12 kDa form conserved almost its full phospholipase activity. In the absence of bile slats both native and 12kDa SPLA2 failed to catalyse the hydrolysis of PC emulsion. When bile salts were pre-incubated with the substrate, the native kinetic protein remained linear for more than 25 min, whereas the 12 kDa form activity was found to decrease rapidly. Furthermore, The SPLA2 activity was dependent on Ca2+; other cations (Mg2+, Mn2+, Cd2+ and Zn2+) reduced the enzymatic activity notably, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca2+.Although marine and mammal pancreatic PLA2 share a high amino acid sequence homology, polyclonal antibodies directed against SPLA2 failed to recognize mammal PLA2 like the dromedary pancreatic one. Further investigations are needed to identify key residues involved in substrate recognition responsible for biochemical differences between the 2 classes of phospholipases.Phopholipases A2 (PLA2s) are esterases that catalyse the hydrolysis of acyl groups at the sn-2 position of glycero-phospholipids (PL) and produce free fatty acids, such as arachidonic acid, and lyso-PL by an interfacial activation catalytic mechanism [1].A large number of distinct PLA2s have been characterized and classified into the broad categories of intracellular and secreted forms of the enzyme. Intracellular (cytosolic) PLA2s participate in cellular eicosanoid metabolism and signal transduction. Numerous isoforms of secretory phospholipases (sPLA2s) have been identified and divided into several gr
Immunohistochemical localization of hepatopancreatic phospholipase in gastropods mollusc, Littorina littorea and Buccinum undatum digestive cells
Zied Zarai, Nicholas Boulais, Pascale Marcorelles, Eric Gobin, Sofiane Bezzine, Hafedh Mejdoub, Youssef Gargouri
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-219
Abstract: We have previously producted an antiserum reacting specifically with mSDPLA2. It labeled zymogen granules of the hepatopancreatic acinar cells and the secretory materials of certain epithelial cells in the depths of epithelial crypts in the hepatopancreas of snail. To confirm this localization a laser capture microdissection was performed targeting stained cells of hepatopancreas tissue sections. A Western blot analysis revealed a strong signal at the expected size (30 kDa), probably corresponding to the PLA2.The present results support the presence of two hepatopancreatic intracellular and extracellular PLA2 in the prosobranchs gastropods molluscs, Littorina littorea and Buccinum undatum and bring insights on their localizations.Snails require lipids for metabolic energy and for maintaining the structure and integrity of cell membranes in common with other animals to tolerate environemental strains [1]. The analyses of lipid composition of digestive gland and pedal muscle of two northern freshwater pulmonate snails Lymnaea stagnalis and Lymnaea ovata and three marine prosobranch gastropods Littorina obtusata, Littorina littorea and Buccinum undatum from the White Sea, shown that the content of triacylglycerides both in digestive gland and pedal was higher in littoral dwellers Littorina, the activity of which depends on the tide level. The presence of massive shell enhances demands in energy needed for supporting movement and activity. Because the intensity of energy metabolism is related to quantity of total phospholipids, mitochondria and activity of their oxidizing ferments, the presence of thick shell in marine snails together with motor activity costs more in terms of energy than in freshwater snails with thin shell [1].In different molluscs, food is processed to varying degrees as it passes through the alimentary tract. It is generally assumed that digestion of ingested material takes place in two phases, an extracellular process and intracellular digestion, w
Immunohistochemical localization of hepatopancreatic phospholipase A2 in Hexaplex Trunculus digestive cells
Zied Zarai, Nicholas Boulais, Aida Karray, Laurent Misery, Sofiane Bezzine, Tarek Rebai, Youssef Gargouri, Hafedh Mejdoub
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-91
Abstract: The marine snail digestive phospholipase A2 (mSDPLA2) has been previously purified from snail hepatopancreas. The specific polyclonal antibodies were prepared and used for immunohistochimical and immunofluorescence analysis in order to determine the cellular location of mSDPLA2. Our results showed essentially that mSDPLA2 was detected inside in specific vesicles tentatively named (mSDPLA2+) granules of the digestive cells. No immunolabelling was observed in secretory zymogene-like cells. This immunocytolocalization indicates that lipid digestion in the snail might occur in specific granules inside the digestive cells.The cellular location of mSDPLA2 suggests that intracellular phospholipids digestion, like other food components digestion of snail diet, occurs in these digestive cells. The hepatopancreas of H. trunculus has been pointed out as the main region for digestion, absorption and storage of lipids.The Muricidae family of snails includes about 1,000 species, which represent a diverse and important component of marine communities [1]. The banded murex, Hexaplex trunculus (Linnaeus, 1758), is found in the mediterranean sea and adjacent atlantic ocean from the Portuguese coast, southward to Morocco and to the Madeira and Canary islands [2] and [3]. This specie is a commercially important marine snail in the mediterranean coasts.The digestive gland or the hepatopancreas of gastropod molluscs like the marine snail H. trunculus is the key organ for metabolism. It is the main source of production of digestive enzymes, and it is involved in absorption of nutrients, food storage and excretion [4]. It combines many functions of the liver, pancreas, intestine and other organs in vertebrates [5]. For this reason, it has captivated scientists for more than 180 years [6] and [7] and it was considered as an excellent model for food digestion and cell secretion [8]. Its primary role is the synthesis and secretion of digestive enzymes, swallowing and final digestion of the in
The in-vitro evaluation of antibacterial, antifungal and cytotoxic properties of Marrubium vulgare L. essential oil grown in Tunisia
Zied Zarai, Adel Kadri, Ines Ben Chobba, Riadh Ben Mansour, Ahmed Bekir, Hafedh Mejdoub, Néji Gharsallah
Lipids in Health and Disease , 2011, DOI: 10.1186/1476-511x-10-161
Abstract: The agar disk diffusion method was used to study the antibacterial activity of M. vulgare essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC50) were investigated to characterize the antimicrobial activities of this essential oil. The in vitro cytotoxicity of M. vulgare essential oil was examined using a modified MTT assay; the viability and the IC50 were used to evaluate this test.The antimicrobial activity of the essential oil was investigated in order to evaluate its efficacy against the different tested microorganisms. The present results results showed a significant activity against microorganisms especially Gram (+) bacteria with inhibition zones and minimal inhibitory concentration values in the range of 6.6-25.2 mm and 1120-2600 μg/ml, respectively, whereas Gram (-) bacteria exhibited a higher resistance. As far as the antifungal activity, among four strains tested, Botrytis cinerea exhibited the strongest activity with inhibition zones of 12.6 mm. However, Fusarium solani, Penicillium digitatum and Aspergillus niger were less sensitive to M. vulgare essential oil. About the citotoxicity assay, this finding indicate the capability of this essential oil to inhibited the proliferation of HeLa cell lines under some conditions with IC50 value of 0.258 μg/ml.This investigation showed that the M. vulgare essential oil has a potent antimicrobial activity against some Gram (+) pathogenic bacteria and Botrytis cinerea fungi. The present studies confirm the use of this essential oil as anticancer agent. Further research is required to evaluate the practical values of therapeutic applications.The Lamiaceae plants was considered as one of the large plant families used as a framework to evaluate the occurrence of typical secondary metabolites [1]. The genus Marrubium comprises 10 species, which are found wild in many regions of Tunisia.
Dirichlet Brownian Motions  [PDF]
Hafedh Faires
Open Journal of Statistics (OJS) , 2014, DOI: 10.4236/ojs.2014.411085
Abstract: In this work we introduce a Brownian motion in random environment which is a Brownian constructions by an exchangeable sequence based on Dirichlet processes samples. We next compute a stochastic calculus and an estimation of the parameters is computed in order to classify a functional data.
The Stochastic Error Rate Estimation of Prediction Distributions  [PDF]
Hafedh Faires
Journal of Mathematical Finance (JMF) , 2015, DOI: 10.4236/jmf.2015.52016
Abstract: The estimation of claims reserves is usually done by applying techniques called IBNR techniques within a stochastic framework. The main objective of this paper is to predict the partial reserve and to estimate the error rate of prediction distributions by using the stochastic model proposed in [1].
Existence and Uniqueness of Strong Solution for Shear Thickening Fluids of Second Grade
Hafedh Bousbih,Mohamed Majdoub
Mathematics , 2014,
Abstract: In this paper we study the equations governing the unsteady motion of an incompressible homogeneous generalized second grade fluid subject to periodic boundary conditions. We establish the existence of global-in-time strong solutions for shear thickening flows in the two and three dimensional case. We also prove uniqueness of such solution without any smallness condition on the initial data or restriction on the material moduli.
Transient analysis of lossy multiconductor transmission lines model based by the characteristics method
Youssef MEJDOUB,Hicham ROUIJAA,Abdelilah GHAMMAZ
International Journal of Engineering and Technology , 2011,
Abstract: In this paper, we will present a low losses multiconductor transmission lines model valid both in the time and the frequency domains. This model is an extension of the characteristics method (Branin method) valid for lossless lines. Our model permits to describe the line as a quadripole whose advantage is to avoid the presupposed applied charges conditions in its extremes. This permits it to be easily introduced in the circuit simulators such as Spice, Esacap and Saber, and it is valid both in time and frequency domains. Diverse examples of applications products by the literature are presented to validate these method and to show their interests.
The dynamic field in turbulent round jet discharging into a co-flowing stream  [PDF]
Mohamed Hichem Gazzah, Nejmiddin Boughattas, Hafedh Belmabrouk, Rachid Said
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.26079
Abstract: The effects of a co-flow on a spreading and entrainment rate of turbulent round jets have been studied numerically. The first and second order closure models are used and have been comp- ared with existing experimental data. The influence of theses models on the dynamic fields is examined. The results of the models in general agree well with the trends observed experiment- tally. The co-flowing imposed noticeable restri- ctions on the spreading and the turbulent mixing. Finally, an entrainment hypothesis has been introduced to describe the development of turbulent jets issuing into a stagnant or co-flowing air. It relates the mass flow rate of the surround- ing fluid entrained into the jet to the characteristic velocity difference between the jet and the co-flow. It is obvious that the co-flow decreases considerably the entrainment of air.
Phase Transfer Catalysis of Henry and Darzens Reactions  [PDF]
Layla Mhamdi, Hafedh Bohli, Younes Moussaoui, Ridha ben Salem
International Journal of Organic Chemistry (IJOC) , 2011, DOI: 10.4236/ijoc.2011.13018
Abstract: We describe in this work the influence of the addition of phase transfer catalyst in heterogeneous medium liquid/liquid on the output of the reactions of Darzens and Henry. It proves that the reaction of Darzens is favoured in the presence of low base such as K2CO3 and Et3N. Phase transfer catalysis is an efficient activation method in Darzens and Henry reactions. Thus, the Ethylene Diammonium Diacetate (EDD) has a comparable catalytic activity has that of quaternary ammonium salts in the reaction of Darzens.
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