Publications by authors named "Anne Ravel"

27 Publications

  • Page 1 of 1

Management of isolated non-traumatic renal artery dissection: report of four cases.

Acta Radiol 2012 May 19;53(4):401-5. Epub 2012 Apr 19.

Department of Radiology, Clermont Ferrand University Hospital, Université D'Auvergne, France.

Background: Isolated non-traumatic renal artery dissection (RAD) is a rare disorder with uncertain natural history. The management may be surgical reconstruction, endovascular repair, or conservative medical treatment, yet no official consensus had been established.

Purpose: To report the management of four cases of isolated non-traumatic RAD, emphasizing the beneficial role of conservative medical treatment.

Material And Methods: From the year 2000 till 2011, four male patients with mean age of 42.5 years (range 34-48 years) presented with isolated non-traumatic RAD and were initially treated with medical therapy. Transcatheter in situ thrombolysis was performed in a case with thrombotic occlusion.

Results: Isolated non-traumatic RAD in four patients involving at least seven branches progressed to thrombotic occlusion in two branches, luminal narrowing in five, dual lumens in two, and aneurysmal dilatation in three. Medical treatment was efficacious in three patients, who showed persistent preserved renal function, controlled blood pressure, and favorable arterial remodeling. After failure of medical therapy, the fourth patient was referred to surgery. Thrombolysis was successful to dissolute an occluding thrombotic dissection.

Conclusion: Conservative therapy is safe and effective when the renal artery is patent and blood pressure is controlled: we propose it as the first line of treatment, reserving interventional management for refractory cases.
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http://dx.doi.org/10.1258/ar.2012.110303DOI Listing
May 2012

Endovascular treatment of eight renal artery aneurysms.

Acta Radiol 2012 May 20;53(4):430-4. Epub 2012 Mar 20.

Department of Radiology, Clermont Ferrand University Hospital, Université D'Auvergne, France.

Background: Renal artery aneurysms (RAA) are a relatively rare vascular entity. Treatment could be either surgical or via an endovascular route. The main aim of therapy is to prevent lethal rupture.

Purpose: To evaluate the angiographic and clinical results after endovascular treatment (EVT) of eight renal artery aneurysms.

Material And Methods: From January 2000 to June 2011, 18 patients presented with 18 renal artery aneurysms. One was classified as Rundback type I, 15 were type II, and two aneurysms were type III. Endovascular treatment was considered unsafe in 10 cases (all were Rundback type II), and were referred to surgery. The remaining eight aneurysms were treated endovascularly during altogether nine sessions. Among these, four patients were asymptomatic, three were hypertensive, and one presented with ipsilateral flank pains. Aneurysmal sac diameter varied between 12 and 50 mm. EVT included selective coil embolization in five cases, covered stents in two cases, and parent artery occlusion in one.

Results: Follow-up with CT angiography was obtained in all endovascularly treated aneurysms (range 6-54 months, mean 15 months). Complete durable occlusion was achieved in all aneurysms except one, which showed re-expansion after 20 months and was retreated with covered stent implantation. Clinically silent, branch occlusion occurred after four procedures with subsequent limited (less than 25%) ischemic parenchymal loss. All patients were discharged with preserved renal function. Clinical improvement was noted in all symptomatic patients.

Conclusion: Endovascular treatment of renal artery aneurysms is an adequate treatment and can be proposed, if feasible, as first step.
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http://dx.doi.org/10.1258/ar.2012.110458DOI Listing
May 2012

[Acute aortic syndrome and endovascular treatment: good indications of stent-graft, stent and aortic fenestration].

Presse Med 2011 Jan 3;40(1 Pt 1):62-71. Epub 2010 Dec 3.

Centre hospitalier universitaire, pôle d'imagerie, service de radiologie B, Université d'Auvergne Clermont 1, faculté de médecine, EA 3295, BP 38, 63001 Clermont-Ferrand cedex 1, France.

Acute aortic syndrome of the descending aorta can be treated with stent-graft thanks to technical and material development. Ruptured aneurysms, aortic dissection, wall hematoma and penetrating ulcers can be treated with stent-graft. According to the type of initial lesion, and the clinical tolerance, the emergency of treatment can be different. Non covered stent and aortic fenestration are used in case of visceral ischemia in aortic dissection, according to the type of ischemia.
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http://dx.doi.org/10.1016/j.lpm.2010.10.013DOI Listing
January 2011

Revascularization of traumatic renal artery dissection by endoluminal stenting: three cases.

Acta Radiol 2010 Feb;51(1):21-6

Radiology B, CHU G Montpied, Clermont-Ferrand, France.

Traumatic injury of renal arteries is rare and can induce renal dysfunction and hypertension. Management options include observation, nephrectomy, surgical repair, and, more recently, percutaneous angioplasty. We report three cases of renal artery thrombosis occurring in young multitrauma patients (mean age 28.7 years) treated with stenting. Immediate satisfactory results were obtained in all cases. Postprocedure anticoagulant and antiplatelet treatment were given according to associated contraindicating lesions. During follow-up, in-stent restenosis occurred in one patient and was treated successfully with a second stenting procedure. No renal dysfunction or hypertension was observed after 28.6 months follow-up. Percutaneous angioplasty is a valuable alternative to surgical treatment in selected patients.
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http://dx.doi.org/10.3109/02841850903473314DOI Listing
February 2010

Chiral ligand-exchange chromatography of amino acids using porous graphitic carbon coated with a dinaphthyl derivative of neamine.

Anal Bioanal Chem 2009 Jan 9;393(2):655-60. Epub 2008 Nov 9.

Département de Pharmacochimie Moléculaire UMR 5063 CNRS, Institut de Chimie Moléculaire de Grenoble FR 2607, Université Grenoble I (Joseph Fourier), UFR de Pharmacie, 38041, Grenoble cedex 9, France.

In this paper, we describe the preparation and the evaluation of a porous graphitic carbon (PGC) column coated with a new dinaphthyl derivative of neamine for chiral ligand-exchange (LE) chromatography. It was shown that the graphitic surface/dinaphthyl anchor system efficiently (1.15 micromol/m(2)) and stably (three months of intensive use) adsorbs the neamine template onto the chromatographic support. The resulting coated PGC stationary phase showed appreciable LE-based enantioselective properties towards several native amino acids.
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http://dx.doi.org/10.1007/s00216-008-2488-8DOI Listing
January 2009

Reversal of the enantiomeric elution order of some aromatic amino acids using reversed-phase chromatographic supports coated with the teicoplanin chiral selector.

Talanta 2006 Jan 10;68(3):1032-6. Epub 2005 Aug 10.

Département de Pharmacochimie Moléculaire UMR 5063 CNRS, Institut de Chimie Moléculaire de Grenoble FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Domaine de la Merci, La Tronche, France.

In this paper, two chiral stationary phases were prepared by coating the surface of both C8 and C18 high-performance liquid chromatography (HPLC) supports with the teicoplanin chiral selector. The hydrophobic C11 acyl side chain, attached to the D-glucosamine group of teicoplanin, served as anchor moiety for the immobilization of the chiral selector on the apolar support material. The retention and enantioselectivity of these coated stationary phases were studied using some aromatic amino acids as probe solutes and an aqueous solution as mobile phase. It was found that the enantiomer elution order on the modified C8 and C18 stationary phases was reversed (L>D) relatively to that classically observed with a teicoplanin covalently immobilized on a silica support (D>L). Such a dynamic coating on the reversed-phase supports was found to be of interest since the apparent enantioselectivity was not significantly changed by the use during an extended period of time or following a long-term storage of the columns.
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http://dx.doi.org/10.1016/j.talanta.2005.07.009DOI Listing
January 2006

[Vascular interventional procedures in oncology].

Bull Cancer 2007 Feb;94(2):147-59

Service de radiologie B, hôpital Gabriel-Montpied, BP 69, 63003 Clermont-Ferrand, Inserm Erim EA 3295 ERI 14, F, CHU, 63000 Clermont-Ferrand.

Indications for interventional radiology have increased, and various arterial and venous procedures are nowadays possible in oncology. Besides emergency procedures, scheduled palliative or curative procedures require multidisciplinary cooperation emphasizing on cautions related to iodine contrast media and concerning immunosuppresion, hemostasis disorders, analgesia, and the choice of the adequate approach. Diagnostic endovascular biopsies and venous sampling may be performed. Embolisation procedures are useful for achieving hemostasis, tumor devascularisation, or chemo-embolisation. Revascularisation procedures concern central vein obstructions, catheter occlusion or arterial stenoses and occlusions. Vena cava filtering, retrieval of intravascular foreign bodies and percutaneous implantation of ports can also be indicated, as well other treatments of central venous access complications. The principles, technical aspects, results, and indications of these various endovascular procedures are described in this review.
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February 2007

Palliative transarterial embolization of renal tumors in 20 patients.

Int Urol Nephrol 2007 20;39(1):47-50. Epub 2007 Feb 20.

Department of Urology, University Hospital, CHU G. Montpied BP 69, 63000 Clermont-Ferrand, France.

Objectives: The aim of this study is to evaluate immediate technical and clinical results of palliative transarterial renal embolization in patients with symptomatic renal tumors.

Methods: Parenchymal embolization of 20 renal tumors was performed in 20 symptomatic patients with hematuria and/or lumbar pain and/or para-neoplastic syndrome. Seven patients were inoperable because of poor general condition, and 15 patients had metastatic lesions.

Results: Immediate technical success was observed, with post-infarction pain in all patients requiring analgesia in 12 cases (which was successful in 90%); 8 patients had transitory fever. With a median follow up of 8.1 (range 4-27) months, recurrent hematuria was noted in two patients for which partial embolization was initially chosen; pain did not recur in any patients.

Conclusions: Palliative embolization of advanced symptomatic renal tumors is easy to accomplish with low morbidity. It helps to alleviate invalidating symptoms in a multidisciplinary management of advanced renal tumors.
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http://dx.doi.org/10.1007/s11255-006-9072-yDOI Listing
November 2007

Chiral resolution of histidine using an anti-D-histidine L-RNA aptamer microbore column.

J Chromatogr B Analyt Technol Biomed Life Sci 2007 Jan 25;845(2):186-90. Epub 2006 Jul 25.

Département de Pharmacochimie Moléculaire UMR 5063 CNRS, Institut de Chimie Moléculaire de Grenoble FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

In this paper, we report a new anti-amino acid aptamer chiral stationary phase (CSP). The enantiomers of histidine were separated using an immobilized histidine-specific L-RNA aptamer (40-mer) and an aqueous buffer as mobile phase. The effects of the variation of different operating parameters, including the mobile phase pH and the MgCl2 concentration as well as the column temperature, on the solute retention were assessed. The results suggested that (i) the protonated form of histidine was involved in the stereospecific RNA binding and (ii) Mg2+ was essential for the target enantiomer binding to the specific aptamer sites. From a practical point of view, it appeared that the baseline resolution in a minimum analysis time can be achieved at a column temperature of 35 degrees C for an eluent containing 10 mM of MgCl2, pH 5.5.
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http://dx.doi.org/10.1016/j.jchromb.2006.06.026DOI Listing
January 2007

Enantiomeric separation using an l-RNA aptamer as chiral additive in partial-filling capillary electrophoresis.

Anal Chem 2006 May;78(9):3032-9

Département de Pharmacochimie Moléculaire, UMR 5063 CNRS, ICMG FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

In this paper, we report the chiral resolution of arginine using an anti-arginine l-RNA aptamer chiral selector in partial-filling CE. The effects of the capillary temperature, sample load, and aptamer plug length on the enantiomeric separation were assessed. Very high chiral resolving capability was observed at low or moderate capillary temperatures (the target peak being not detected in the separation window), whereas the practical chiral resolution was achieved only at high enough temperatures (50-60 degrees C). Over this high-temperature range, the electrophoretic behavior of the target enantiomer appeared to result from a combination of binding site heterogeneity, slow desorption kinetics, and concentration overload of aptamer binding sites. From additional thermal UV melting experiments, three RNA conformations were identified for the 50-60 degrees C temperatures. It was suggested that the presence of these different RNA conformations was a plausible source of the binding site heterogeneity.
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http://dx.doi.org/10.1021/ac060033iDOI Listing
May 2006

A L-RNA aptamer chiral stationary phase for the resolution of target and related compounds.

J Chromatogr A 2005 May;1076(1-2):62-70

Département de Pharmacochimie Moléculaire UMR 5063 CNRS, Institut de Chimie Moléculaire de Grenoble FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

In this paper, we report for the first time an aptamer-based chiral stationary phase (CSP) able to resolve racemates of both target and various related compounds. The enantiomers of tyrosine and analogues (11 enantiomeric pairs) were separated using an immobilized tyrosine-specific L-RNA aptamer as CSP and an aqueous buffer (8 mM Tris-HCl buffer, 25 mM NaCl, 5 mM MgCl2; pH 7.4) as mobile phase, at a column temperature of 10 degrees C. It appeared that the carboxylic and amino groups as well as the aromatic side chain of amino acid controlled the stereospecific recognition. Modifications on the polar groups were strongly detrimental for enantioselectivity while the replacement of the phenolic group by some bicyclic aromatic residues of different polarity, size or shape did not impair the enantioselective interaction. In addition, the effects of the mobile phase composition and column temperature upon the retention and stereoselective properties of the CSP were assessed. Finally, it was found that the immobilized RNA aptamer could be used under hydro-organic mobile phase conditions without alteration of the stationary phase stability.
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http://dx.doi.org/10.1016/j.chroma.2005.03.132DOI Listing
May 2005

Thermodynamic origin of the chiral recognition of tryptophan on teicoplanin and teicoplanin aglycone stationary phases.

J Sep Sci 2005 Mar;28(5):409-20

Département de Pharmacochimie Moléculaire, UMR 5063 CNRS, ICMG FR 2607, UFR de Pharmacie, Université Joseph Fourier, Grenoble, France.

The D-, L-tryptophan binding and the chiral recognition properties of the teicoplanin and teicoplanin aglycone (TAG) chiral stationary phase (CSPs) were compared at various column temperatures. The solute adsorption isotherms (bi-Langmuir model) were determined for both the two CSPs using the perturbation method. It was demonstrated that the sugar units were involved in the reduction of the apparent enantioselectivity through two phenomena: (i) the inhibition of some enantioselective contacts with low-affinity binding regions of the aglycone and (ii) a decrease in the stereoselective properties of the aglycone high-affinity binding pocket. The phenomenon (ii) was governed by both a decrease in the ratio of the enantiomer adsorption constant and a strong reduction of the site accessibility for D- and L-tryptophan. In addition, a temperature effect study was performed to investigate the chiral recognition mechanism at the aglycone high-affinity pocket. An enthalpy-entropy compensation analysis derived from the Grunwald model as well as the comparison with the literature data demonstrated that the enantioselective binding mode was dependent on an interface dehydration process. The change in the enantioselective process observed between the TAG and teicoplanin CSP was characterized by a difference of ca. 2-3 ordered water molecules released from the species interface.
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http://dx.doi.org/10.1002/jssc.200400043DOI Listing
March 2005

Chiral stationary phase based on a biostable L-RNA aptamer.

Anal Chem 2005 Apr;77(7):1993-8

Département de Pharmacochimie Moléculaire UMR 5063 CNRS, Institut de Chimie Moléculaire de Grenoble FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

An immobilized anti-L-arginine d-RNA aptamer, used as a target-specific chiral stationary phase (CSP), was found to be very quickly degraded by RNases under usual chromatographic utilization and storage. To overcome this severe limitation for a practical use, a CSP based on the L-RNA aptamer, that is, the mirror image of the D-RNA aptamer, was created. It was shown that this mirror-image approach was a very simple and powerful strategy to develop a highly stable stationary phase due to the intrinsic insensitivity of l-RNA to the RNase degradation. In addition, such an approach allowed one to reverse the enantiomer elution order relative to that obtained with the corresponding d-RNA CSP.
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http://dx.doi.org/10.1021/ac048344lDOI Listing
April 2005

Endovascular treatment of chronic mesenteric ischemia: results in 14 patients.

Cardiovasc Intervent Radiol 2004 Nov-Dec;27(6):637-42. Epub 2004 Oct 6.

Radiology Department, University Hospital, Clermont-Ferrand, France.

We evaluated immediate and long-term results of percutaneous transluminal angioplasty (PTA) and stent placement to treat stenotic and occluded arteries in patients with chronic mesenteric ischemia. Fourteen patients were treated by 3 exclusive celiac artery (CA) PTAs (2 stentings), 3 cases with both Superior Mesenteric Artery (SMA) and CA angioplasties, and 8 exclusive SMA angioplasties (3 stentings). Eleven patients had atheromatous stenoses with one case of an early onset atheroma in an HIV patient with antiphospholipid syndrome. The other etiologies of mesenteric arterial lesions were Takayashu arteritis (2 cases) and a postradiation stenoses (1 case). Technical success was achieved in all cases. Two major complications were observed: one hematoma and one false aneurysm occurring at the brachial puncture site (14.3%). An immediate clinical success was obtained in all patients. During a follow-up of 1-83 months (mean: 29 months), 11 patients were symptom free; 3 patients had recurrent pain; in one patient with inflammatory syndrome, pain relief was obtained with medical treatment; in 2 patients abdominal pain was due to restenosis 36 and 6 months after PTA, respectively. Restenosis was treated by PTA (postirradiation stenosis), and by surgical bypass (atheromatous stenosis). Percutaneous endovascular techniques are safe and accurate. They are an alternative to surgery in patients with chronic mesenteric ischemia due to short and proximal occlusive lesions of SMA and CA.
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http://dx.doi.org/10.1007/s00270-004-0225-zDOI Listing
May 2005

Streptavidin chiral stationary phase for the separation of adenosine enantiomers.

J Chromatogr A 2004 May;1036(2):155-60

Département de Pharmacochimie Moléculaire UMR 5063 CNRS-UJF, Equipe de Chimie Analytique, Université Joseph Fourier, ICMG FR 2607, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

In this paper, a microbore column packed with streptavidin particles was used, at various temperatures (0-24 degrees C), to separate the adenosine enantiomers by HPLC. Using an aqueous mobile phase, the apparent enantioseparation was high for a small molecule, varying from 11.5 at 0 degrees C to 6.2 at 24 degrees C. From the experiments carried out with a streptavidin-biotin complex stationary phase, it was demonstrated that the blockage of the biotin sites of the immobilized streptavidin was responsible for a strong decrease in the enantioselectivity via a direct and/or an indirect effect. From the analysis of the concentration dependencies of the solute retention factor, it was also shown that a reduction of the D-adenosine specific binding sites occurred at the lowest temperature. The thermodynamic parameters determined from the van't Hoff plots indicated that the D-adenosine binding to the streptavidin specific sites was enthalpically driven.
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http://dx.doi.org/10.1016/j.chroma.2004.02.083DOI Listing
May 2004

Immobilized DNA aptamers as target-specific chiral stationary phases for resolution of nucleoside and amino acid derivative enantiomers.

Anal Chem 2004 Feb;76(4):1015-20

Equipe de Chimie Analytique, Département de Pharmacochimie Moléculaire UMR 5063 CNRS-UJF, ICMG FR 2607, Université Joseph Fourier, UFR de Pharmacie de Grenoble, Avenue de Verdun, 38240 Meylan, France.

Recently, we described the use of a DNA aptamer as a new target-specific chiral stationary phase (CSP) for the separation of oligopeptide enantiomers (Michaud, M.; Jourdan, E.; Villet, A.; Ravel, A.; Grosset, C.; Peyrin, E. J. Am. Chem. Soc. 2003, 125, 8672). However, from a practical point of view, it was fundamental to extend the applicability of such target-specific aptamer CSP to the resolution of small (bioactive) molecule enantiomers. In this paper, immobilized DNA aptamers specifically selected against D-adenosine and L-tyrosinamide were used to resolve the enantiomers by HPLC, using microbore columns. At 20 degrees C, the adenosine enantioseparation was similar to that classically reported with imprinted CSPs (approximately 3.5) while a very high enantioselectivity was observed for the tyrosinamide enantiomers (the nontarget enantiomer was essentially nonretained on the CSP). The influence of temperature on solute binding and chiral discrimination was analyzed. The binding enthalpic contributions were determined from linear van't Hoff plots. Very large DeltaH values were obtained for the target enantiomers (-71.4 +/- 0.7 kJ/mol for D-adenosine and -139.4 +/- 2.0 kJ/mol for L-tyrosinamide). Such values were consistent with the formation of a tight complex between these analytes and the aptamer CSPs. This work demonstrates that target-specific aptamer CSPs constitute a powerful tool for the resolution of small (bioactive) molecule enantiomers.
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http://dx.doi.org/10.1021/ac035090fDOI Listing
February 2004

Role of the vancomycin-ristocetin heterodimerization on the enantioselectivity of D,L-tryptophan and D,L-dansyl tryptophan.

J Chromatogr B Analyt Technol Biomed Life Sci 2003 Sep;795(1):115-21

Département de Pharmacochimie Moléculaire, UFR de Pharmacie de Grenoble, Domaine de la Merci, 38700 La Tronche, France.

In this paper, a chromatographic system using immobilized ristocetin as chiral stationary phase and vancomycin as chiral mobile phase additive (CMPA) was described in order to investigate the role of the glycopeptide heterodimerization on the retention and enantioselectivity of D,L-tryptophan and D,L-dansyl tryptophan. A simplified interaction model was derived considering the formation of heterodimers between immobilized ristocetin and vancomycin. This theoretical approach was convenient to describe adequately the retention behavior. When the CMPA concentration increased, the solute retention factor increased for all the solute enantiomers studied indicating that the vancomycin adsorbed on the immobilized ristocetin played a preponderant role in the retention. The D,L-tryptophan enantioselectivity on the dynamically modified stationary phase was improved by a factor of 1.3, probably due to a glycopeptide conformational change upon heterodimerization. On the other hand, a decrease in the chiral discrimination of D,L-dansyl tryptophan was observed. Such a behavior seems to result from the antagonist enantioselective properties of the two glycopeptides for the dansyl amino acids.
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http://dx.doi.org/10.1016/s1570-0232(03)00553-1DOI Listing
September 2003

A DNA aptamer as a new target-specific chiral selector for HPLC.

J Am Chem Soc 2003 Jul;125(28):8672-9

Equipe de Chimie Analytique, Département de Pharmacochimie Moléculaire (UMR 5063 CNRS-UJF), ICMG FR 2607, UFR de Pharmacie de Grenoble, Université Joseph Fourier, Avenue de Verdun, 38240 Meylan, France.

In this paper, a DNA aptamer, known to bind stereospecifically the D-enantiomer of an oligopeptide, i.e., arginine-vasopressin, was immobilized on a chromatographic support. The influence of various parameters (such as column temperature, eluent pH, and salt concentration) on the L- and D-peptide retention was investigated in order to provide information about the binding mechanism and then to define the utilization conditions of the aptamer column. The results suggest that dehydration at the binding interface, charge-charge interactions, and adaptive conformational transitions contribute to the specific D-peptide-aptamer complex formation. A very significant enantioselectivity was obtained in the optimal binding conditions, the D-peptide being strongly retained by the column while the L-peptide eluted in the void volume. A rapid baseline separation of peptide enantiomers was also achieved by modulating the elution conditions. Furthermore, it was established that the aptamer column was stable during an extended period of time. This work indicates that DNA aptamers, specifically selected against an enantiomer, could soon become very attractive as new target-specific chiral selectors for HPLC.
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http://dx.doi.org/10.1021/ja034483tDOI Listing
July 2003

Study of tryptophan enantiomer binding to a teicoplanin-based stationary phase using the perturbation technique. Investigation of the role of sodium perchlorate in solute retention and enantioselectivity.

J Chromatogr A 2003 Jan;986(1):45-53

Equipe de Chimie Analytique, Département de Pharmacochimie Moléculaire, UMR 5063 CNRS-UJF, UFR de Pharmacie de Grenoble, Domaine de la Merci, 38700 La Tronche, France.

The retention of D,L-tryptophan enantiomers on an immobilized teicoplanin column was investigated in relation to the mobile phase sodium perchlorate concentration using the perturbation method to determine the solute distribution isotherms. From the experimental data, it appeared that the bi-Langmuir model was able to describe D- and L-enantiomer retention on the immobilized selector over the salt concentration range. An increase in the apparent enantioselectivity with an increase in sodium perchlorate concentration was observed. The chiral recognition enhancement was governed by (i) an increase in the difference of the adsorption constants for binding to the high-affinity site (aglycone pocket) between the two enantiomers and (ii) enhancement of the number of aglycone chiral regions interacting with D-tryptophan. It is suggested that an ion-pair formation mechanism between perchlorate and solute and/or selector is responsible for this behavior. In addition, this work shows that additional secondary sites on the teicoplanin surface are involved in the apparent enantioselectivity at low sodium perchlorate concentrations.
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http://dx.doi.org/10.1016/s0021-9673(02)01952-0DOI Listing
January 2003

Percutaneous transluminal angioplasty of dysplastic stenoses of the renal artery: results on 70 adults.

Cardiovasc Intervent Radiol 2003 Jan-Feb;26(1):46-51. Epub 2002 Dec 20.

Radiology Department, University Hospital, BP 69-63003 Clermont-Ferrand, France.

Purpose: Retrospective analysis of the dilatation (PTRA) of renal arterial dysplastic stenosis (RADS).

Methods: Seventy patients suffering from hypertension (87 RADS) were treated at our institution for medial (83%) or non-classified fibrodysplasias (17%). Four patients suffered from renal insufficiency. Two endoprostheses were implanted. We evaluated blood pressure with the USCSRH criteria and renal insufficiency with the Martin criteria.

Results: Ninety-five percent technical success and 87.9% clinical success for blood pressure were obtained, with worse results for patients older than 57 years or with a history of hypertension greater than 9 years. Results were better when the RADS was responsible for an ipsilateral renal atrophy or for poorly controlled hypertension. No renal insufficiency worsened during the follow-up.

Conclusion: PTRA is a first-line treatment for renovascular hypertension caused by RADS. The results were encouraging despite a high average age of the subjects and frequent associated extrarenal vascular lesions.
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http://dx.doi.org/10.1007/s00270-002-1797-0DOI Listing
July 2003

Salt effects on the interaction of an amphiphilic model molecule with immobilized phosphatidylcholine monolayers.

J Chromatogr A 2002 Nov;977(2):185-92

The retention of hydrocortisone (used as an amphiphilic model solute) on an immobilized artificial membrane (IAM) column was investigated in relation to the mobile phase concentration of three sodium salts (representing different rankings in the Hofmeister series, i.e. perchlorate, chloride and sulfate) in order to provide insight into the nature of the solute interactions with phospholipid monolayers. The influence of the salt series on solute retention was found to follow the Hofmeister series, emphasizing the role of hydrophobic effect in the solute retention mechanism on phospholipid monolayers. Retention models based on the extended Wyman relations (preferential interaction theory) were developed to analyze more quantitatively the salt effects on the hydrocortisone retention factor. This analysis as well as additional thermodynamic study suggested that the hydrocortisone binding to IAM involved both an insertion into the hydrophobic inside governed by hydrophobic effects and contacts with the interfacial region implying interactions such as van der Waals interactions/hydrogen bonds between the solute hydroxyl groups and the polar headgroups of phospholipidmonolayers.
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http://dx.doi.org/10.1016/s0021-9673(02)01352-3DOI Listing
November 2002

Vancomycin dimerization and chiral recognition studied by high-performance liquid chromatography.

Anal Chem 2002 Oct;74(20):5205-11

Département de Pharmacochimie Moléculaire, UMR CNRS 5063, UFR de Pharmacie de Grenoble, La Tronche, France.

The retention and separation of D,L-dansylvaline enantiomers (used as test solutes) were investigated using silica gel as stationary phase and vancomycin as chiral mobile-phase additive. A retention model was developed to describe the mechanistic aspects of the interaction between solute and vancomycin in the chromatographic system. It considered the formation of vancomycin dimers both "free" in the mobile phase and adsorbed on silica. By fitting the model equation to experimental data, it appeared clearly that the approach taking into account the vancomycin dimerization described accurately the retention behavior of the compounds. The examination of the model equation parameters showed that the glycopeptide dimerization increased the enantioselectivity by a factor of approximately 3.7. This study demonstrated the preponderant role of the vancomycin dimerization on the chiral recognition process of D,L-dansylvaline. Also, an additional analysis on a vancomycin chiral stationary phase indicated that the addition of vancomycin in the mobile phase promoted a greater enantioselectivity mediated by the formation of dimers in the stationary phase.
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http://dx.doi.org/10.1021/ac0257243DOI Listing
October 2002

Chromatographic determination of the association constants between nimesulide and native and modified beta-cyclodextrins.

J Pharm Biomed Anal 2002 Jul;29(3):425-30

Laboratoire de Chimie Analytique, UFR de Pharmacie, Domaine de la Merci, 38700 La Tronche, France.

The retention of a non-steroidal anti-inflammatory drug (NSAID), i.e. nimesulide, in high performance liquid chromatography (HPLC) was investigated using a phenyl bond silica column and beta-cyclodextrin (beta-CD) or hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as mobile phase additive (0-10 mM). Such a study was carried out in order to determine the most efficient cyclodextrin as a potential drug complexing agent for a future application in pharmaceutical formulation. Assuming a 1:1 stoichiometry, the association constants (K) were calculated from the chromatographic data. At a column temperature of 25 degrees C and in a highly aqueous medium (98% phosphate buffer-2% methanol (v/v)), K was equal to 523 and 1285 M(-1) for the nimesulide-beta-CD and nimesulide HP-beta-CD complexes, respectively. These results were consistent with the data reported previously using phase solubility studies and UV spectrophotometry. As well, the thermodynamic parameters of the inclusion complexes were determined from linear van't Hoff plots for the two inclusion complexes. From the enthalpy and entropy changes, it appeared that nimesulide interact more strongly with HP-beta-CD due to a significant hydrophobic effect between the compound and the flexible hydroxypropyl groups.
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http://dx.doi.org/10.1016/s0731-7085(02)00088-2DOI Listing
July 2002

Displacement study on a vancomycin-based stationary phase using N-acetyl-D-alanine as a competing agent.

J Chromatogr Sci 2002 Feb;40(2):83-6

Laboratoire de Chimie Analytique, UFR de Pharmacie de Grenoble, UJF, La Tronche, France.

The analysis of the binding data of D,L-dansyl amino acids on a vancomycin stationary phase is investigated in relation to the addition of N-acetyl-D-alanine in the mobile phase. This eluent additive acts as a specific competing agent for the aglycone pocket of the immobilized chiral selector. A model taking into account both stereoselective and nonstereoselective interactions between the solutes and the stationary phase is used to fit the experimental data. From the results, the theoretical approach is considered to be adequate to describe the competing agent dependence on solute retention. To the best of our knowledge, this report constitutes the first example of a displacement study on a macrocyclic antibiotic stationary phase. This work shows that dansyl amino acids bind to the active aglycone pocket of the selector and that this interaction is enantioselective. The results also demonstrate that additional enantioselective sites at the vancomycin surface are involved in the chiral discrimination of these solutes.
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http://dx.doi.org/10.1093/chromsci/40.2.83DOI Listing
February 2002

A framework based on the extended Wyman concept for analyzing the salt effects on the solute retention in high-performance affinity chromatography.

Anal Chem 2002 Jan;74(1):282-7

Laboratoire de Chimie Analytique, UFR de Pharmacie de Grenoble, UJF, Domaine de la Merci, La Tronche, France.

The analysis of binding data of a ligand to a macromolecule in the presence of an additive can be classically formulated in terms of the linked functions of Wyman. In the case of a salt, this approach has been extended by Tanford such that the contributions of both salt and water are taken into account. In this paper, the extended Wyman theory was applied to high-performance affinity chromatography (HPAC) in order to define a general model describing the effects of the mobile-phase salts on the ligand binding. Various HPAC literature data, as well as our data concerning dansyl amino acid retention on a vancomycin stationary phase, were examined in relation to this model. From the results, this theoretical approach was considered to be adequate to describe accurately the salt dependence on solute retention. This work shows the importance of taking into account the effects of both ionic species and water in the investigation of relative contributions of the interactions involved in the ligand binding to immobilized receptor.
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http://dx.doi.org/10.1021/ac010696uDOI Listing
January 2002
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