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Biomedical subjects

S Guyot

Publications and source records attributed to S Guyot.

13 recordsLinked to original sources
PubMed2006

Iron availability and consumption of tea, vervain and mint during weaning in Morocco.

BACKGROUND/AIMS: Iron deficiency impairs growth and psychomotor development of infants. In Morocco, infusions are introduced very early in infant diet, and could contribute to iron deficiency, due to their high polyphenol content. METHODS: The availability of tea, mint and vervain infusions was assessed using an in vitro model of digestion and dialysis. Two gastric pHs were used: pH 4 as in the first week life, and pH 2.5 as in older infants. Six repetitions of each experiment were made. The total polyphenol content of infusions was measured. RESULTS: At pH 4 and at pH 2.5, iron availability was decreased by tea and vervain, and increased by mint and ascorbic acid. At both pHs it was increased by addition of ascorbic acid to tea and vervain. In addition, at pH 2.5 it was increased by addition of ascorbic acid to mint. The highest value was observed in the presence of both ascorbic acid and mint (33.1 +/- 4.1%). In any case, iron availability was higher at pH 2.5 than at pH 4 (with single compounds or combinations with ascorbic acid). The polyphenol contents (mg/l) of tea, vervain and mint infusions were 2,236.1, 771.1, and 16.5. CONCLUSIONS: Tea and vervain infusions inhibited iron availability. In contrast, mint improved it; vitamin C helped in preventing these inhibiting properties. It could be proposed to discourage tea and vervain drinking at early weaning and to replace them by mint infusion, or at least to promote the consumption of vitamin C-rich fruit juice to counteract these inhibiting effects.

Ascorbic Acid↗
PubMed2004

Non-covalent interaction between procyanidins and apple cell wall material: Part I. Effect of some environmental parameters.

The adsorption of procyanidins on cell wall material were quantified by bringing into contact a solution of procyanidins and a suspension of cell wall material. The influence of structural features such as degree of polymerisation (DP) and percentage of galloylation (% gall), and of physico-chemical parameters such as pH, ionic strength, temperature and presence of ethanol were investigated. The amount of procyanidins bound to the cell wall increased with the DP, the % gall, and the proportion of (+)-catechin, the last indicating an effect of the stereochemistry of the flavan-3-ols. Complex formation between procyanidins and cell wall material was not affected by pH in the range 2.2-7 but it was decreased by urea, dioxane and ethanol. Adsorption increased with increasing ionic strength and decreased with increasing temperature. This indicated that the bonds which governed the interaction between procyanidins and cell wall material were weak energy bonds of the type hydrogen bond and hydrophobic interaction.

Adsorption↗
PubMed2004

Chemometric characterisation of Basque and French ciders according to their polyphenolic profiles.

Polyphenolic compositions of Basque and French ciders were determined by HPLC-DAD following thiolysis, in order to characterise and differentiate these beverages and then develop a classification system capable of confirming the authenticities of both kinds of cider. A data set consisting of 165 cider samples and 27 measured features was evaluated using multivariate chemometric techniques, such as cluster analysis and principal component analysis, in order to perform a preliminary study of data structure. Supervised pattern recognition techniques such as linear discriminant analysis (LDA), K-nearest neighbours (KNN), soft independent modelling of class analogy (SIMCA), and multilayer feed-forward artificial neural networks (MLF-ANN) attained classification rules for the two categories using the chemical data, which produced satisfactory results. Authentication systems obtained by combining two of these techniques were proposed. We found that SIMCA and LDA or KNN models achieved 100% hit-rates, since LDA and KNN permit the detection of every Basque cider and SIMCA provides a model for Basque cider that excludes all French ciders. Polyphenolic profiles of the ciders provided enough information to be able to develop classification rules for identifying ciders according to their geographical origin (Basque or French regions). Chemical and organoleptic differences between these two types of cider are probably due to the original and distinctive cidermaking technologies used for their elaboration. Using polyphenic profiles, about 80% of French ciders could be distinguished according to their region of origin (Brittany or Normandy). Although their polyphenolic profiles did not provide enough information to achieve an authentication system for Breton and Norman ciders.

Journal Article↗
PubMed2004

Detection of phenolic oxidation products in cider apple juice by high-performance liquid chromatography electrospray ionisation ion trap mass spectrometry.

Juice was prepared from cider apples of the cultivar "Kermerrien" under oxidative conditions. After isolation by solid-phase extraction, the phenolic fraction was subjected to high-performance liquid chromatography/electrospray ionisation mass spectrometry. SIM scans were performed at m/z values obtained in model solutions. The oxidation products, resulting from coupling between a molecule of caffeoylquinic acid and caffeoylquinic acid, catechin or dimeric flavan-3-ol, were detected.

Beverages↗
PubMed2001

Interactions between apple cell walls and native apple polyphenols: quantification and some consequences.

Cell walls were prepared from apple parenchyma by a phenol:buffer procedure. Polyphenols were extracted from freeze-dried apple parenchyma by methanol and water:acetone, and purified by preparative HPLC. Interactions were quantified by bringing into contact suspended cell walls and polyphenol solutions. Hydroxycinnamic acids and (-)-epicatechin did not bind to cell walls. Binding of procyanidins was fast and reached up to 0.6 g per g cell walls. The amounts of procyanidins bound increased with the initial concentration and with DPn. Procyanidins could be partially desorbed by buffer, more being desorbed in the presence of dissolved cell wall polysaccharides. They were totally desorbed using 8 M urea or acetone:water. Higher polymers were bound selectively from procyanidin mixtures, and very high average DPn were obtained in extensively washed complexes. Binding of procyanidins inhibited enzymic degradation of the cell walls.

Adsorption↗
PubMed2001

Thiolysis-HPLC characterization of apple procyanidins covering a large range of polymerization states.

Procyanidins from the cortex of two cider apple varieties (Malus domestica; Kermerrien and Avrolles) were extracted by solvents. After a solid-phase extraction step, they were fractionated by normal- or reversed-phase HPLC at the semipreparative scale to obtain a series of purified fractions covering a wide range of polymerization states. Freeze-dried fractions were characterized by reversed-phase HPLC following thiolysis. Elution on normal-phase HPLC gave oligomeric procyanidins fractions with (average degree of polymerization) values varying from 2 to 8, whereas polymeric fractions ( values varying from 7 to 190) were obtained by reversed-phase HPLC. Constitutive units were mainly (-)-epicatechin with a proportion above 95% for all fractions. Thiolysis yields were wholly homogeneous with an average value of 75%, which indicates that the efficiency of the reaction did not depend on the polymerization state of the procyanidin fractions.

Antioxidants↗
PubMed2000

An improved anion-exchange HPLC method for the detection and purification of adenoviral particles.

We have developed an anion-exchange high-performance liquid chromatography (HPLC) method using Q Sepharose XL (Amersham Pharmacia Biotech) as adsorbent to analyze samples containing adenovirus. This method has several major advantages over the HPLC method previously described for quantitating particles, namely (1) a >10-fold improvement in the detection limit of adenovirus in crude preparations; (2) absence of interferences originating from nucleic acids and proteins which usually contaminate crude samples; (3) unprecedented sharpness and symmetry of adenovirus peak, rendering the identification of the viral peak unambiguous, even in extremely crude and dilute preparations; and (4) no enzymatic treatment required even for crude samples. This assay was used to quantitate particles in samples taken at the transfection and amplification stages of production of various recombinant adenovirus, and in cultures of wild-type adenovirus of different serotypes. A modification of this analytical method was also developed for the purification of infectious adenovirus particles, including fiber-modified and third-generation recombinant viruses, giving highly purified preparations from low-titer crude lysates with an excellent overall recovery (50-74%).

Adenoviridae↗
PubMed1999

Polyphenol profiles of French cider apple varieties (Malus domestica sp.).

The cortex of 14 French apple varieties (12 cider and 2 juice varieties), one English cider variety, and one dessert apple (i.e., Golden Delicious) were studied for their polyphenol composition. Total polyphenols were assayed by the Folin-Ciocalteu method, and the precise polyphenolic composition (monomeric catechins, proanthocyanidins, hydroxycinnamic acids, and dihydrochalcones) was obtained by HPLC following thiolysis. ESI-MS and ESI-MS/MS analyses showed that chlorogenic acid and p-coumaroylquinic acid were methylated under the conditions of thiolysis. Depending on the variety, the global polyphenol concentration varied from 1 to 7 g per kilogram of fresh cortex. Cider varieties globally showed a higher polyphenol concentration than the dessert apple Golden Delicious, bitter varieties being the more concentrated. The proportion of the polyphenol classes varied greatly from one cultivar to another. For all varieties, procyanidins were always the predominant class. They were mainly constituted of (-)-epicatechin units with a small proportion of (+)-catechin as a terminal unit. The average degree of polymerization ranged between 4.2 and 7.5 depending upon the variety with an exception for the sharp varieties Guillevic and Avrolles which showed significant concentrations of procyanidins with DPn of 40 and 50, respectively.

Beverages↗
PubMed1999

5'-flanking and intragenic sequences confer androgenic and developmental regulation of mouse aldose reductase-like gene in vas deferens and adrenal in transgenic mice.

The MVDP (mouse vas deferens protein) gene, which encodes an aldose reductase-like enzyme, is mainly expressed in vas deferens epithelium and adrenal cortex. Vas deferens MVDP gene transcription was known to be under androgenic control, we now have evidence for androgen and probable ACTH responsiveness of the MVDP gene in the adrenal. To analyze the role of potential regulatory regions in hormonal, developmental, and tissue-specific aspects of MVDP regulation, we generated transgenic mice harboring MVDP-CAT fusion genes. The constructs carried either -1.8 or -0.5 kb 5'-flanking sequence attached to the chloramphenicol acetyltransferase gene in presence or absence of a 3.5-kb intragenic fragment in a downstream position. We show that at least two regions ensure proper gene regulation in vivo. The first, located within the 1.8-kb promoter fragment, directs tissue specificity; positive elements necessary for vas deferens and adrenal expression lay within positions -1804 to -510 and -510 to +41, respectively. The second, located within the 3.5-kb intragenic fragment spanning intron 1 to intron 2, increases percentage of expressing lines and behaves as a vas deferens-specific enhancer. Hormonal and developmental control of transgenes closely parallel endogenous gene regulation. Androgen and ACTH responsiveness in adrenals is conferred by 0.5-kb promoter, whereas in vas deferens, full androgenic response of the 1.8-kb promoter required the 3.5-kb intragenic fragment. Thus, vas deferens and adrenals use distinct cis-acting elements to direct and regulate the expression of the MVDP gene.

Adrenal Glands↗
PubMed1998

Occluding aortic endoluminal stent graft combined with extra-anatomic axillofemoral bypass as alternative management of abdominal aortic aneurysms for patients at high risk with complex anatomic features: a preliminary report.

PURPOSE: To describe an exclusion endoluminal technique for management of abdominal aortic aneurysms among high-risk patients with complex anatomic features. METHODS: From January 1995 to December 1996, among 143 patients with infrarenal abdominal aortic aneurysm treated by means of endograft placement, 9 (6.3%) had complex aortic or aortoiliac morphologic features. For these patients, the endograft was delivered through a femoral cutdown in an occluding aortoiliac configuration. The contralateral iliac artery was occluded with an iliac endograft. Axillofemoral bypass grafting was performed. Computed tomographic scans were obtained regularly. RESULTS: There was 1 postoperative death of severe arrhythmia. All aneurysms were found to be affected by thrombosis on immediately postoperative computed tomographic scans, except in 1 patient with a proximal leak, which was managed successfully with angiographic embolization. The mean follow-up time was 12 months. Aortic aneurysm diameter decreased from 2 mm at 6 months (2 patients) to 6 mm at 12 months (6 patients). All axillofemoral bypass grafts are patent. CONCLUSIONS: Placement of an occluding endograft associated with axillofemoral bypass grafting is a good alternative for patients at high risk with complex anatomic features. Longer-term follow-up study is needed to evaluate this endoluminal technique.

Aged↗
PubMed1996

[Treatment of abdominal aortic aneurysm by application of a Corvita endoprosthesis. Medium-term results of a feasibility study].

Despite improvements in surgical techniques, progress in anesthesia and hemodynamic control, the risk of fatal outcome in the standard surgical technique for aneurysms of the abdominal aorta remains at about 5 to 6% due to associated coronary and pulmonary lesions. Surgical access to the aneurysm may also be hindered in patients with a past history of multiple abdominal operations. In collaboration with the Corvita company, we developed a modular endoprosthesis for endoluminal treatment of AAA and report the results of a feasibility study.

Aortic Aneurysm, Abdominal↗
PubMed1996

[Percutaneous gastrostomy in interventional radiology in cervico-facial oncology. Apropos of 174 cases].

We report a series of 174 percutaneous gastrostomies implanted in our interventional radiology unit in patients with cancer of the upper airway and upper digestive tract: two localizations, hypopharynx and oropharynx comprised 68% of the cases (106/174). Tumor stage had reached palliative treatment in 80 cases, was in the initial phase of treatment in 57 cases and was in a sequelae phase after treatment in 37 cases. Despite problems related to anatomic modifications and tumor volume or sequelae of prior or ongoing treatment, we did not record any failures. The rate of minor complications was 15%. The one severe complication (peritonitis) required laparotomy. The duration of enteral nutrition via the gastrostomy varied from 3 weeks to more than 3 years. There were no long-term complications. We thus suggest that interventional percutaneous gastrostomy is a useful alternative to endoscopic percutaneous gastrostomy or the nasoesophageal tube, particularly in patients with voluminous tumors restricting the hypopharynx and oropharynx.

Adult↗