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21.
The venoms of Viperidae snakes contain numerous serine proteinases that have been recognized to possess one or more of the essential activities of thrombin on fibrinogen and platelets. Among them, a platelet proaggregant protein, cerastocytin, has been isolated from the venom of the Tunisian viper Cerastes cerastes. Using the RACE-PCR technique, we isolated and identified the complete nucleotide sequence of a cDNA serine proteinase precursor. The recombinant protein was designated rCC-PPP (for C. cerastes platelet proaggregant protein), since its deduced amino acid sequence is more than 96% identical to the partial polypeptide sequences that have been determined for natural cerastocytin. The structure of the rCC-PPP cDNA is similar to that of snake venom serine proteinases. The expression of rCC-PPP in Escherichia coli system allowed, for the first time, the preparation and purification of an active protein from snake venom with platelet proaggregant and fibrinogenolytic activities. Purified rCC-PPP efficiently activates blood platelets at nanomolar (8 nM) concentrations, as do natural cerastocytin (5 nM) and thrombin (1 nM). It is able to clot purified fibrinogen and to hydrolyze alpha-chains. Thus, rCC-PPP could be therefore considered a cerastocytin isoform. By comparison with other snake venom serine proteinases, a Gly replaces the conserved Cys(42). This implies that rCC-PPP lacks the conserved Cys(42)-Cys(58) disulfide bridge. A structural analysis performed by molecular modeling indicated that the segment of residues Tyr(67)-Arg(80) of rCC-PPP corresponds to anion-binding exosite 1 of thrombin that is involved in its capacity to induce platelet aggregation. Furthermore, the surface of the rCC-PPP molecule is characterized by a hydrophobic pocket, comprising the 90 loop (Phe(90)-Val(99)), Tyr(172), and Trp(215) residues, which might be involved in the fibrinogen clotting activity of rCC-PPP. 相似文献
22.
TGF-beta-dependent mechanisms mediate restoration of self-tolerance induced by antibodies to CD3 in overt autoimmune diabetes 总被引:23,自引:0,他引:23
CD3-specific antibodies have the unique capacity to restore self-tolerance in established autoimmunity. They induce long-term remission of overt diabetes in nonobese diabetic (NOD) mice and in human type I diabetes. The underlying mechanisms had been unclear until now. Here we report that treatment with CD3epsilon-specific antibodies induces transferable T-cell-mediated tolerance involving CD4+CD25+ cells. However, these CD4+CD25+ T cells are distinct from naturally occurring regulatory T cells that control physiological autoreactivity. CD3-specific antibody treatment induced remission in NOD Cd28-/- mice that were devoid of such regulatory cells. Remission of diabetes was abrogated by coadministration of a neutralizing transforming growth factor (TGF)-beta-specific antibody. The central role of TGF-beta was further suggested by its increased, long-lasting production by CD4+ T cells from tolerant mice. These data explain the intriguing tolerogenic effect of CD3-specific antibodies and position them as the first clinically applicable pharmacological stimulant of TGF-beta-producing regulatory CD4+ T cells. 相似文献
23.
Mosbah H Sayari A Mejdoub H Dhouib H Gargouri Y 《Biochimica et biophysica acta》2005,1723(1-3):282-291
The Staphylococcus xylosus strain secretes a non-induced lipase in culture medium: S. xylosus lipase (SXL). Pure SXL is a monomeric protein (43 kDa). The 23 N-terminal amino acid residues were sequenced. This sequence is identical to that of Staphylococcus simulans lipase (SSL); in addition, it exhibits a high degree of homology with Staphylococcus aureus lipase (SAL NCTC 8530) sequences. The cloning and sequencing of gene part encoding the mature lipase shows one nucleotide difference with SSL, which corresponds to the change of one residue at a position 311. The lipase activity is maximal at pH 8.2 and 45 degrees C. SXL is able to hydrolyse triacylglycerols without chain length specificity. The specific activity of about 1900 U/mg was measured using tributyrin or triolein as substrate at pH 8.2 and at 45 degrees C in the presence of 2 mM CaCl2. In contrast to some previously characterized staphylococcal lipases, Ca2+ is not required to trigger the activity of SXL. SXL was found to be stable between pH 5 and pH 8.5. The enzyme maintains 50% of its activity after a 15-min incubation at 60 degrees C. Using tripropionin or vinyl esters as substrates, SXL does not present the interfacial activation phenomenon. Unlike many lipases, SXL is able to hydrolyse its substrate in the presence of bile salts or amphiphilic proteins. SXL is a serine enzyme, which is inhibited by THL. 相似文献
24.
Delphine Delample Fabienne Durand Arnold Severac Monia Belghith Emilie Mas Francoise Michel 《Free radical research》2013,47(9):807-814
Objective: The aim of this study was to determine the implication of xanthine oxidase (XO) in the exercise-induced muscle oxidative stress and muscle dysfunction of these patients.Methods: A randomized, crossover and double-blind study was conducted in nine severe COPD patients, who performed a localized quadriceps endurance test after oral treatment with allopurinol, a XO inhibitor or placebo. Redox status was studied in arterial and venous femoral blood before and after the endurance test.Results: In placebo condition, muscle exercise resulted in a significant increase in AOPP and isoprostanes, with a significant increase in the venoarterial difference (v-a) in isoprostanes after exercise as compared with before (p<0.05). In contrast, allopurinol treatment prevented the elevation in AOPP levels and v-a isoprostanes after exercise. However, no significant improvement in quadriceps muscle endurance was observed, but allopurinol treatment seemed to preserve muscle strength properties.Conclusion: This study demonstrates that XO is implicated in the exercise-induced muscle oxidative stress of COPD patients. Allopurinol administration seemed to improve only some muscle properties. Therefore other sources of muscle oxidative stress should be implicated in muscle dysfunction observed in these patients. 相似文献
25.
Edith C. Hammer Hafedh Nasr Jan Pallon Pål Axel Olsson Håkan Wallander 《Mycorrhiza》2011,21(2):117-129
We investigated the elemental composition of spores and hyphae of arbuscular mycorrhizal fungi (AMF) collected from two saline
sites at the desert border in Tunisia, and of Glomus intraradices grown in vitro with or without addition of NaCl to the medium, by proton-induced X-ray emission. We compared the elemental
composition of the field AMF to those of the soil and the associated plants. The spores and hyphae from the saline soils showed
strongly elevated levels of Ca, Cl, Mg, Fe, Si, and K compared to their growth environment. In contrast, the spores of both
the field-derived AMF and the in vitro grown G. intraradices contained lower or not elevated Na levels compared to their growth environment. This resulted in higher K:Na and Ca:Na ratios
in spores than in soil, but lower than in the associated plants for the field AMF. The K:Na and Ca:Na ratios of G. intraradices grown in monoxenic cultures were also in the same range as those of the field AMF and did not change even when those ratios
in the growth medium were lowered several orders of magnitude by adding NaCl. These results indicate that AMF can selectively
take up elements such as K and Ca, which act as osmotic equivalents while they avoid uptake of toxic Na. This could make them
important in the alleviation of salinity stress in their plant hosts. 相似文献
26.
Najla Trabelsi Hanen Falleh Ines Jallali Alia Ben Daly Hafedh Hajlaoui Abderrazek Smaoui Chedly Abdelly Riadh Ksouri 《Acta Physiologiae Plantarum》2012,34(1):87-96
Changes in phenolic composition and biological activities were investigated in different Limoniastrum monopetalum L. organs. For that, 80% aqueous acetone extracts were used to estimate total phenolic contents and their antioxidant activities
were evaluated using DPPH· and O2·− radical scavenging activities and reducing power. The efficiency of organ extracts was tested against human pathogen strains.
Ultimately, acid hydrolysis of all organs was subjected to RP-HPLC for phenolic identification. Results showed that flower
extracts exhibited the highest polyphenol (65.42 GAE/g DW) and flavonoid (35.36 CE/g DW) contents. Stems were enriched in
condensed tannin content (21.4 mg CE/g DW) and displayed the best antiradical activities and the highest reducing power. Besides,
stem and gall extracts showed the highest efficiency against pathogenic bacteria as compared with those of flower. Concerning
the antifungal test, a slight activity was found in gall extracts. The RP-HPLC showed a difference in phenolic compounds that
varied as function of organ. In fact, the major phenolic compound varied as function of organ. Results suggest that L. monopetalum could be a promising source of biomolecules for therapeutic and nutraceutical industries and the difference between organs
may be related to their physiological role. 相似文献
27.
Hammadi Fakhfakh Abdelkader Bouhlel Hafedh Ketata Ahmed Sahnoun Ali Bahloul Mohamed Nabil Mhiri 《Andrologie》2005,15(2):242-244
Lymphangioma is a benign tumor of the lymphatic system classified as simple, cavernous, or cystic depending on the size of the dilated lymphatic spaces within the tumor. Most cases present as a soft, cystic, slowly enlarging swelling in the neck and axilla in children, while the scrotum is a rare site. We report the case of a 39-year-old man who presented with a painless left hemiscrotal mass. On examination, the testes and spermatic cords were normal bilaterally. There was a firm, polycystic mass in the inferior portion of the left hemiscrotum. Scrotal ultrasound revealed normal testes, with a large complex cystic loculated mass. Histology demonstrated a cystic lymphangioma. The mass was completely excised. The patient remained well without recurrence with a follow-up of 6 months. 相似文献
28.
Influence of static magnetic field on cadmium toxicity: Study of oxidative stress and DNA damage in rat tissues 总被引:1,自引:0,他引:1
Salem Amara Hafedh Abdelmelek Catherine Garrel Pascale Guiraud Thierry Douki Jean-Luc Ravanat Alain Favier Mohsen Sakly Khmais Ben Rhouma 《Journal of trace elements in medicine and biology》2006,20(4):263-269
In the present study, we investigated the effect of co-exposure to static magnetic field (SMF) and cadmium (Cd) on the biochemical parameters, antioxidant enzymes activity and DNA damage in rat tissues. Animals were treated with cadmium (CdCl2, 40 mg/L, per os) in drinking water during 4 weeks. Cd treatment induced an increase of plasma lactate dehydrogenase (LDH) and transaminases levels. Moreover, Cd treatment increased malondialdehyde (MDA) and 8-oxodGuo levels in rat tissues. However, the antioxidant enzymes activity such as the glutathione peroxidase (GPx), catalase (CAT) and the superoxide dismutase (SOD) were decreased in liver and kidney, while we noted a huge increase of hepatic and renal cadmium content. Interestingly, the combined effect of SMF (128mT, 1 h/day during 30 consecutive days) and Cd (40 mg/L, per os) decreased the GPx and CAT activities in liver compared to cadmium treated group. However, the association between SMF and Cd failed to alter transaminases, MDA and 8-oxodGuo concentration.
Cd treatment altered antioxidant enzymes and DNA in liver and kidney of rats. Moreover, SMF associated to Cd disrupt this antioxidant response in liver compared to Cd-treated rats. 相似文献
29.
Mohamed Guerfali Ines Maalej Ali Gargouri Hafedh Belghith 《Journal of Molecular Catalysis .B, Enzymatic》2009,57(1-4):242-249
The present study explores the efficiency of Talaromyces thermophilus β-xylosidase, in the production of xylose and xylooligosaccharides. The β-xylosidase was immobilized by different methods namely ionic binding, entrapment and covalent coupling and using various carriers. Chitosan, pre-treated with glutaraldehyde, was selected as the best support material for β-xylosidase immobilization; it gave the highest immobilization and activity yields (94%, 87%, respectively) of initial activity, and also provided the highest stability, retaining 94% of its initial activity even after being recycled 25 times. Shifts in the optimal temperature and pH were observed for the immobilized β-xylosidase when compared to the free enzyme. The maximal activity obtained for the immobilized enzyme was achieved at pH 8.0 and 53 °C, whereas that for the free enzyme was obtained at pH 7.0 and 50 °C. The immobilized enzyme was more thermostable than the free β-xylosidase. We observed an increase of the Km values of the free enzyme from 2.37 to 3.42 mM at the immobilized state. Native and immobilized β-xylosidase were found to be stimulated by Ca2+, Mn2+ and Co2+ and to be inhibited by Zn2+, Cu2+, Hg2+, Fe2+, EDTA and SDS. Immobilized enzyme was found to catalyze the reverse hydrolysis reaction, forming xylooligosaccharides in the presence of a high concentration of xylose. In order to examine the synergistic action of xylanase and β-xylosidase of T. thermophilus, these two enzymes were co-immobilized on chitosan. A continuous hydrolysis of 3% Oat spelt xylan at 50 °C was performed and better hydrolysis yields and higher amount of xylose was obtained. 相似文献
30.
Mohamed Guerfali Moncef Chaabouni Ali Gargouri Hafedh Belghith 《Applied microbiology and biotechnology》2010,85(5):1361-1372
This study is an application of an experimental design methodology for the optimization of the culture conditions of α-l-arabinofuranosidase production by Talaromyces thermophilus. Wheat bran and yeast extract were first selected as the best carbon and nitrogen sources, respectively, for enzyme production.
A Plackett–Burman design was then used to evaluate the effects of eight variables. Statistical analyses showed that while
pH had a negative effect on α-l-arabinofuranosidase production, wheat bran and MgSO4 had a significantly positive effect. The values of the latter three parameters were further optimised using a central composite
design and a response surface methodology. The experimental results were fitted to a second-order polynomial model that yielded
a determination coefficient of R
2 = 0.91. The statistical output showed that the linear and quadric terms of the three variables had significant effects. Using
optimal conditions, the experimental value of α-l-arabinofuranosidase activity produced was very close to the model-predicted value. The optimal temperature and pH of enzyme
activity were 55 °C and 7.0, respectively. This enzyme was very stable over a considerable pH range from 4 to 9. The crude
enzyme of T. thermophilus rich in α-l-arabinofuranosidase was also used for saccharification of lignocellulosic materials and arabinose production. 相似文献