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A Duchateau

Publications and source records attributed to A Duchateau.

At least 19 recordsLinked to original sources
PubMed2003

Design and synthesis of fluorescent beta-cyclodextrins for the enantioselective sensing of alpha-amino acids.

Fluorescent monofunctionalized beta-cyclodextrins bearing a copper(II) binding side arm and a dansyl group (CD-NH-AA-CH(2)CH(2)NH-DNS) were designed as enantioselective sensors for unmodified alpha-amino acids. The side arm was derived from amino acid synthons (AA = L- and D-phenylalanine (1 and 2), L- and D-phenylglycine (3 and 4), L-proline (5), and L-cyclohexylglycine (6)) and was chosen in order to contain an amide, an amine, and a sulphonamide group. Enantioselectivity was evaluated by addition of copper(II) complexes of D- or L-valine and D- or L-proline. Chiral discrimination in the fluorescence response was observed in all cases, due to a ligand exchange process. The best conditions for these experiments were found to be the use of an excess (10:1) of the copper complex. The cyclodextrin 4 containing a D-phenylglycine unit was found to be poorly enantioselective, as found for 2, suggesting that the best design can be obtained by using L-amino acids. All L-amino acid containing cyclodextrins showed good enantioselectivities, some of which were higher than those already reported for 1. Other analytes related to amino acids were studied using cyclodextrins 1 and 3. Enantiomers of alpha,alpha-disubstituted amino acids, N-methylamino acids, and amino acid amides were found to be discriminated, while beta-phenylalanine and other molecules bearing a poor anchoring group at the alpha-carbon gave poor enantioselectivity. On the basis of the present data a model for the recognition process, based on the formation of ternary diastereomeric complexes, is proposed.

Amino Acids↗
PubMed1998

Factors influencing corpus argyrophil cell density and hyperplasia in reflux esophagitis patients treated with antisecretory drugs and controls.

A cross sectional study was designed to elucidate the factors influencing the argyrophil cell population in patients with gastroesophageal reflux disease treated with omeprazole (N = 201) or H2-receptor antagonists (N = 118) and in control patients (N = 215). Fasting gastrinemia and Helicobacter pylori serology were determined. Gastritis, Helicobacter pylori infection, and argyrophil cell density and hyperplasia were evaluated in gastric biopsies. The argyrophil cell density was higher in both treatment groups than in controls (P = 0.002 and P = 0.051), whereas argyrophil cell hyperplasia was similar in the three groups. According to multivariate analysis, positive Helicobacter pylori serology was an independent parameter that decreased both density and grade of hyperplasia of argyrophil cells. Female gender and hypergastrinemia were independent factors increasing argyrophil cell density and hyperplasia, whereas antisecretory therapy, age and active gastritis were not. In addition, atrophic gastritis independently increased argyrophil cell hyperplasia. The prevalence of atrophic gastritis was significantly higher in Helicobacter pylori-positive than in negative patients and lower in the patients treated long-term with omeprazole than in the other groups.

Adult↗
PubMed1997

[Gastroprotective effect of an antacid coating agent in rats. Role of endogenous prostaglandins, capsaicin-sensitive afferents neurons and nitric oxide].

UNLABELLED: The aims of this study were: a) to demonstrate the gastroprotective effect of the antacid and mucosal coating agent Gastralgine (aluminium hydroxide and glycinate, magnesium trisilicate and simeticone) against ethanol- and indomethacin-induced gastric injury in the rat; b) to investigate whether gastroprotection elicited by this agent involves stimulation of capsaicin sensitive afferent neurons and activation of the nitric oxide system. METHODS: Rats received intragastrically 2 mL of the antacid or distilled water followed 1 hr later by 2 mL of 100% ethanol ig or 30 mg of indomethacin sc. The surface of ethanol-induced lesions and the length of indomethacin-induced lesions were measured. The role of afferent neurons and endogenous nitric oxide in the prevention of ethanol-induced gastric damage was determined using respectively capsaicin and the inhibitor of nitric oxide biosynthesis, NG-nitro-L-arginine. RESULTS: The antacid and mucosal coating agent significantly reduced the area of macroscopic lesions induced by ethanol and the length of lesions induced by indomethacin. Both functional ablation of afferent nerves and inhibition of nitric oxide synthesis significantly increased ethanol-induced gastric injury but failed to reverse the gastroprotective effect of the antacid against 100% ethanol. CONCLUSIONS: The antacid and mucosal coating agent Gastralgine has a gastroprotective effect against ethanol- and indomethacin-induced injury in the rat. This property does not involve stimulation of capsaicin sensitive afferent neurons or synthesis of endogenous nitric oxide.

Animals↗
PubMed1990

Prevention by aluminium phosphate of gastric lesions induced by ethanol in the rat: role of endogenous prostaglandins and sulfhydryls.

This study was designed to demonstrate the cytoprotective effect of an antacid containing aluminium phosphate (Phosphalugel) against ethanol-induced gastric injury in the rat and to determine whether this cytoprotective effect is mediated by endogenous prostaglandins and sulfhydryls. We have quantitatively evaluated gastric mucosal lesions using macroscopic and histological techniques one hour after ethanol administration. Two ml of aluminium phosphate given orally one hour before administration of 2 ml of 100% ethanol significantly (p less than 0.01) reduced the area of macroscopic lesions induced by ethanol (3.3 +/- 0.9%) when compared to distilled water (20 +/- 4.8%). The histological study showed that aluminium phosphate prevented deep tissue necrosis. However, it did not protect surface epithelial cells against ethanol injury. Pretreatment with indomethacin, 5 mg/kg sc one hour before aluminium phosphate, slightly but significantly (p less than 0.05) reduced the cytoprotective effect of aluminium phosphate. Macroscopic lesions occupied 4.3 +/- 0.94% and 1.88 +/- 0.41% of total mucosal area in indomethacin group and in vehicle group, respectively. On the other hand, the sulfhydryl blocker, N-ethyl-maleimide, 10 mg/kg sc, given one hour before aluminium phosphate, completely abolished the cytoprotective effect of aluminium phosphate (32.92 +/- 4.85% in N-ethyl-maleimide group versus 3.78 +/- 1.41% in vehicle group; p less than 0.01). These results show that aluminium phosphate has a cytoprotective effect against ethanol injury in the rat. This property appears to be mediated by both endogenous prostaglandins and sulfhydryls.

Aluminum↗
PubMed1989

Determination of the enantiomers of alpha-amino acids and alpha-amino acid amides by high-performance liquid chromatography with a chiral mobile phase.

A high-performance liquid chromatographic method for the enantiomeric analysis of a mixture of an alpha-amino acid and the corresponding acid amide is described. Reversed-phase chromatography with copper(II) acetate and N,N-di-n-propyl-L-alanine in the mobile phase are used for the separation. For Val and Val-NH2, several parameters affecting retention and enantioselectivity were investigated. The results indicate that by manipulation of pH, ionic strength, temperature, concentration of CuII, N,N-di-n-propyl-L-alanine and ion-pairing reagent, good control of enantiomeric separation can be achieved. For alpha-amino acid amides a mechanism is proposed which may account for the retention and enantioselectivity. Examples of enantiomeric analysis of mixtures of alpha-amino acids and alpha-amino acid amides with aliphatic, aromatic and polar side-chains are given. The method can be used for the control of the enantiomeric purity of alpha-amino acids and the corresponding acid amides obtained by enantioselective synthesis.

Amides↗
PubMed1989

The efficacy of estrus detection and fertility following synchronization with PGF2a or synchro - mate- B in Zebu cattle.

Two experiments were carried out to assess the efficacy of estrus detection and fertility in Zebu cattle after synchronization with prostaglandin F2a or a progestagen. The first experiment compared estrus detection rates and fertility following insemination in 42 cows previously synchronized with either 25 mg of PGF2a or with a 6 mg of Norgestomet implant plus 5 mg i.m. of estradiol valerate (SMB). Differences were observed in the percentage of cows detected in estrus (54 vs 95%, respectively, P < 0.05), but not in fertility at the first synchronized estrus (26 vs 15%), nor in the detection rate and fertility at the subsequent estrous period (38 v 47%). The second experiment evaluated the efficacy of estrus detection at different time intervals in 30 cows, comparing estrus synchronized with PGF2a with the subsequent estrous period. The observation periods were continuous, day and night, for 100 h both after PGF2a treatment and from Day 18 of the treatment cycle (Period 1). In addition, the animals were administered PGF2a again on Day 10 of the second cycle and observed continuously from 0600 to 1800 h, and from Day 18 of the treatment cycle (Period 2). Finally, the same treatment regimen was used except that the observation was between 0600 to 0700 h and 1800 to 1900 h (Period 3). No differences were obtained in the percentage of cows detected in estrus in the synchronized and nonsynchronized groups (average 75%); however, accuracy in the detection of estrus in Period 3 differed in the nonsynchronized and synchronized estrus groups by 40% (P < 0.05) compared with the other two, more intense observation periods.

Journal Article↗
PubMed1989

[Results of weight-loss treatment at a hospital. Significance of the administration of triiodothyronine in small doses during a protein diet].

We report the short-term effects of very-low-calorie liquid formula diet (n = 51) and of 600 Kcalories diet (n = 13) in patients who were hospitalized during 3 weeks. Weight loss averaged 278 +/- 14 g/day (m +/- SEM). It was slightly higher with the very-low-calorie liquid formula diet (293 +/- 21 g vs 242 +/- 25 g, N.S.). Individual weight-loss was unpredictable and highly variable; it ranged from 62 to 636 g/day. During the very-low-calorie formula diet, the expected low T3 syndrome was observed and 12 patients were given T3 (25 micrograms during the second week and 50 micrograms during the third week). These rather small doses corrected T3 values, but lowered total and free T4 levels. T3 administration did not modify the magnitude of weight loss in our patients.

Adult↗
PubMed1989

Protective effect of low dose of enprostil against gastric blood loss induced by aspirin in man.

This study tested the efficacy of enprostil given both at potent antisecretory (35 micrograms twice daily) and weak antisecretory (7 micrograms twice daily) doses in preventing aspirin-induced gastric blood loss measured chemically in gastric washings in 10 volunteers. Aspirin (500 mg four times a day) increased gastric blood loss compared with placebo (p less than 0.001). When enprostil was given in addition to aspirin, gastric blood loss was not significantly different from basal value. The pH of gastric washings was significantly increased by the large but not by the low dose of enprostil compared with placebo. The two doses of enprostil were equally efficacious, suggesting a mucosal protective effect of enprostil independent of acid inhibition.

Adult↗
PubMed1988

Evaluation of sample work-up methods and internal standards for the determination of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid in brain by HPLC with electrochemical detection.

A high-performance liquid chromatographic method with electrochemical detection is described for the determination of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in brain. Results of studies on sample work-up methods and on the use of various internal standards are reported. The reproducibility of determination of 5-HT and 5-HIAA in two regions of rabbit brain has been evaluated.

Journal Article↗
PubMed1987

Selected ion monitoring analysis of monoamine metabolites in cerebrospinal fluid. Application to the study of in vivo effects of alpha 2-antagonists.

The technique of isotope dilution mass spectrometry has been used for the measurement of biogenic amine metabolites in cerebrospinal fluid (CSF). CSF samples were collected from rabbits treated with alpha 2-antagonists. The aim of our study was to determine the specificity of these drugs on the central nervous noradrenergic, dopaminergic and serotonergic activity as measured by the release of corresponding monoamine metabolites. 3-Methoxy-4-hydroxyphenylethylene glycol (MHPG) and vanilmandelic acid (VMA) were used as parameters for the noradrenergic activity, whereas homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) were employed to follow the dopaminergic and serotonergic activity, respectively. For the measurement of the biogenic amine metabolites a published GCMS method has been adapted. Samples of 200 microliters CSF were processed. Following addition of deuterated internal standards and acidification, extraction was carried out with ethyl acetate. Preliminary experiments with the analysis of MHPG using diethyl ether for extraction gave rise to emulsion formation and resulted in poor recoveries for MHPG and in irreproducibility problems due to a preferential extraction of non-labelled MHPG, effects which were not observed with ethyl acetate extraction. Derivatization was done with a mixture of pentafluoropropionic anhydride/pentafluoropropanol (or hexafluoroisopropanol) in order to derivatize both hydroxyl and carboxylic acid groups. The derivatization procedure was optimized for the analysis of 5-HIAA by carrying out a second reaction step with pentafluoropropionic anhydride alone in order to complete the derivatization for the indolic NH moiety. The molecular ions of the derivatized products were selected for detection.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1987

Effects of propranolol and sucralfate on ethanol-induced gastric mucosal damage in chronic portal hypertensive rats.

In a rat model of chronic portal hypertension we studied ethanol-induced gastric mucosal damage and the effects of pretreatment by propranolol and sucralfate. Susceptibility to ethanol was increased in chronic portal hypertensive rats compared with sham-operated rats (55 +/- 8% vs. 25 +/- 4%). Both acute pretreatment (10 min) and chronic pretreatment (3 weeks) with propranolol reduced gastric mucosal injury induced by ethanol in portal hypertensive rats, compared with saline-treated rats. Acute and chronic pretreatment with propranolol had no protective effect in sham-operated rats. In portal hypertensive rats, sucralfate in two different doses (500 and 125 mg/kg) protected the gastric mucosa against ethanol-induced gastric injury compared with animals receiving saline (2 +/- 1% and 3 +/- 2% vs. 25 +/- 3%). Sucralfate at the higher dose did not reduce portal pressure in portal hypertensive rats. We conclude that: (1) chronic portal hypertension increases ethanol-induced gastric damage; (2) acute and chronic propranolol treatment reduces ethanol-induced gastric injury in portal hypertensive rats, probably by decreasing portal hypertension; (3) sucralfate has a cytoprotective effect in portal hypertensive rats without reducing portal pressure. These results suggest a potential application of sucralfate in patients otherwise treated by sclerotherapy.

Animals↗
PubMed1987

The usefulness of fructosamine determination in diabetic patients and its relation to metabolic control.

In 116 diabetics and 101 control subjects, we measured both HbA1 and fructosamine values, neither could definitely separate the 2 populations. We observed an excellent correlation between both variables and between each of them and various other parameters of metabolic control. It appeared that the correlation with recent (4 weeks) diabetes control was better with fructosamine than with HbA1 levels. The opposite was true when a 8 week period was considered. The presence of diabetic complications did not modify the fructosamine levels. These results confirm the value of fructosamine measurement in the evaluation of recent diabetes control, but clearly, HbA1 determination remains the best parameter of long-term glycemic control.

Blood Glucose↗
PubMed1986

Characterization of serotonin receptors and lack of effect of antidepressant therapy on monoamine functions in various regions of the rabbit brain.

The effects of single and long-term administration of the antidepressants imipramine, desimipramine, amitriptyline, zimelidine and maprotiline were studied in the rabbit brain. Special attention was given to the brain serotonin (5-HT) receptors. Our results show that in different areas of the rabbit brain, the binding sites for 5-HT display pharmacological characteristics very similar to those of the 5-HT1 and 5-HT2 receptors described for the rat brain. No significant correlation could be shown between the distribution of either of the receptors and the distribution of serotonergic nerve terminals (as measured by the 5-HT content and the [3H]5-HT accumulation). Addition of antidepressants to rabbit brain slices, in vitro, caused an inhibition of the [3H]5-HT accumulation. The compounds only weakly inhibited the binding of [3H]5-HT and [3H]ketanserin as compared to the inhibition caused by serotonergic agonists and antagonists. The [3H]5-HT accumulation in brain slices was markedly reduced 2 h after a single i.p. injection of imipramine. After a two-week administration of the antidepressants, the specific binding of neither [3H]5-HT nor [3H]ketanserin was significantly altered. The simultaneous determination of monoamine metabolites and of dopamine-beta-hydroxylase in the cerebrospinal fluid of these treated rabbits did not reveal any significant difference from the control animals.

Animals↗
PubMed1985

Fertility trial in Zebu cattle after a natural or controlled estrus with prostaglandin F2 Alpha, comparing natural mating with artificial insemination.

With the object of comparing reproductive efficiency obtained by natural mating and by artificial insemination (AI), not only following a natural estrus but also after an induced estrus with PGF2Alpha in Zebu cattle in the tropics, 244 adult cows were divided into 4 groups. Group I (N = 69) and Group III (n = 62) were injected with 25 mg of PGF2Alpha when a functional CL was found on rectal examination. Group I was inseminated and group III was served by natural mating, both groups within five days after injection. Groups II (n = 57) and IV (n = 56) were left untreated, group II being AI and group IV ran with a fertile bull for 22 days. Estrus detection was carried out only in the injected groups (I and III) for 15 minutes every three hours between 0600 and 1800. All information was analyzed by linear trigonometric models. The onset of estrus occurred on average 68.7 h after injection in group I and 59.5 h in group III. However only 46.3% and 54.8% of animals were detected in estrus in group I and III respectively, the difference being significant (P < 0.10). Conception rates were 18.6%, 29.8%, 19.3% and 33.9% for groups I, II, III, and IV respectively. A significant difference (P < 0.10) existed between the injected groups and the untreated ones.

Journal Article↗