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Biomedical subjects

A Collet

Publications and source records attributed to A Collet.

At least 19 recordsLinked to original sources
PubMed2005

A prospective, randomised, single-blinded, controlled trial comparing two topical anaesthetic modalities for the application of a tenaculum to the cervix.

The aim of this study was to compare the efficacy of equivalent doses of lignocaine spray vs lignocaine jelly in reducing pain during the application of a tenaculum to the cervix. A total of 58 women undergoing hysterosalpingography were prospectively randomised to receive either two doses of 10% lignocaine spray or 1 ml of 2% lignocaine jelly (both doses equivalent to 20 mg of lignocaine base) topically onto the cervix before tenaculum attachment. There was no difference in pain scores (measured by visual analogue scale and 4-point verbal descriptor scale) between lignocaine spray and lignocaine jelly during the attachment of the tenaculum to the cervix. In conclusion, there was no difference in pain during tenaculum attachment to the cervix following topical application of equivalent doses of either lignocaine jelly or spray.

Administration, Intravaginal↗
PubMed2001

Synthesis of deuterium-labeled cryptophane-A and investigation of Xe@cryptophane complexation dynamics by 1D-EXSY-NMR experiments.

We present the synthesis of a series of deuterated cryptophanes 2-6 by a slightly modified procedure used for cryptophane-A. We show that for [Xe@cryptophane] complexes the use of variable-temperature one-dimensional 129Xe magnetization transfer (1D-EX-SY) allows the measurement of exchange rates. From these data the decomplexation activation energy Ea has been estimated to be 37.5+/-2 kJ mol(-1). The decomplexation activation enthalpy, deltaH(++) = 35.5+/-2 kJ mol(-1), and entropy, deltaS(++) = -60+/-5 J mol(-1) K(-1), have also been calculated. The calculated negative activation entropy suggests that the activated complex associated with decomplexation is conformationally more strained than the complex in its ground state.

Journal Article↗
PubMed2001

Molecular polarization and molecular chiralization: The first example of a chiralized xenon atom.

In this article we focus on the interaction between a chiral molecule and a single achiral molecule or an ensemble of achiral molecules. The desymmetrization of the achiral molecules resulting from this interaction is described as "chiralization." By analogy with electric polarization, we factorize chiralization into three factors, i.e., orientation, atomic, and electronic terms. Chiralization depends on the dipolar polarizability of the chiralized molecule but also on polarizabilities of higher order. The experimental part of this work is devoted to the electronic chiralization of a xenon atom and its observation by (129)Xe NMR spectroscopy. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMed2001

Blockade of GRP receptors inhibits gastric emptying and gallbladder contraction but accelerates small intestinal transit.

BACKGROUND & AIMS: This study was designed to characterize [D-F(5)Phe(6)D-Ala(11)]Bn(6-13)OMe (BIM26226) as a gastrin-releasing peptide (GRP)-preferring bombesin receptor antagonist and to determine whether GRP physiologically regulates gastrointestinal motility. Intravenous BIM26226 (5-500 microg. kg(-1). h(-1)) inhibits GRP-induced gallbladder contraction and plasma cholecystokinin (CCK) release in a dose-dependent fashion. METHODS: Gastric emptying and small bowel transit of a solid meal were quantified using scintigraphy. Meal-stimulated gallbladder contraction was measured by sonography in a 2-period crossover design. RESULTS: Intravenous BIM26226 potently inhibited gastric lag time (114 +/- 7 vs. 41 +/- 6 minutes [control]) and gastric emptying rate (0.11 +/- 0.02%/min vs. 0.26 +/- 0.04%/min [control]), whereas concomitant infusion of BIM26226 accelerated small bowel transit time (153 +/- 41 vs. 262 +/- 20 minutes [control]). A continuous liquid meal perfusion into the duodenum induced complete gallbladder contraction (t(50%), 35 +/- 4 minutes), which BIM26226 inhibited significantly (t(50%), 64 +/- 8 minutes). BIM26226 did not alter plasma CCK response, indicating that circulating CCK did not mediate these effects. CONCLUSIONS: These data show that BIM26226 is a potent antagonist of exogenous and endogenous GRP and suggest that GRP is a major physiologic regulator of gastric emptying, small bowel transit, and gallbladder contraction.

Adult↗
PubMed2001

Deep lamellar keratoplasty as surgical management of anterior and posterior segment injuries to the eye.

PURPOSE: To report on the feasibility of combined deep lamellar keratoplasty and vitreoretinal surgery in one patient with corneal opacity associated with retinal detachment. METHODS: A 35-year-old man presented with a major hematocornea and retinal detachment after experiencing a right ocular trauma with corneoscleral wound 1 month earlier. We elected to perform deep lamellar keratoplasty to perform vitreoretinal surgery through the bared Descemet's membrane within the same surgical procedure. RESULTS: Deep lamellar keratoplasty offered perfect visibility of the anterior and posterior segments of the eye through the bared Descemet's membrane during the 4-hour operation. Descemet's membrane was resilient enough to maintain remarkable tightness of the anterior chamber throughout vitreoretinal surgery procedures (vitrectomy, peeling of epiretinal membranes, encircling scleral buckling). Unfortunately, despite our efforts and extended operative time, the retina could not be restored to its position because of the high baseline level of ocular impairment. CONCLUSION: The combined procedure (deep lamellar keratoplasty and pars plana vitrectomy) appeared to be a good and feasible alternative to the temporary keratoprosthesis usually applied in that situation.

Adult↗
PubMed2000

Anastomosis of the ovarian vein to the hepatic portal vein in sheep induces ovarian hyperstimulation associated with increased LH pulsatility, but only in the absence of the contralateral ovary.

In this study, two experiments were performed, the first of which examined the ovarian response in ewes that were subject to unilateral ovariectomy (ULO) at different intervals (0-14 days) after surgical anastomosis (AN) of the ovarian vein to the mesenteric vein (n=7 ewes), or sham operation (SO; n=4 ewes). Hypertrophy and development of multiple follicular and luteal structures on AN ovaries were observed after ULO, while SO ovaries remained of normal size and appearance after ULO. The second experiment involving 11 ewes (five AN; six SO) aimed to clarify the mechanism by which AN following ULO-induced ovarian hypertrophy and increased follicle development. The results confirmed that there were more large (>5 mm) follicles on AN compared with SO ovaries; however, their rate of atresia was similar. Oestradiol and progesterone concentrations in follicular fluid of class 1 follicles (5-9 mm) were higher in AN ovaries than those in control follicles of the same size collected in the late follicular phase of an induced oestrous cycle. In AN ewes, intrafollicular progesterone concentrations increased while follicular aromatase activity and intrafollicular oestradiol, inhibin A, follistatin and activin A concentrations all decreased as follicle size increased. Oestradiol and progesterone concentrations were substantially higher in ovarian venous blood than in hepatic venous blood, both in AN and SO ewes, whereas inhibin A levels were not significantly modified by passage through the liver in either group. Mean plasma LH concentration, and LH pulse frequency and amplitude increased markedly after AN but were not affected by SO. Plasma FSH showed only a small transient increase after AN, presumably due to the maintenance of inhibin feedback. Injection of prostaglandin F(2)(alpha) 4 days later did not further modify LH or FSH secretion in either group. Full ovariectomy (FO) 9-14 days after AN or SO increased LH secretion markedly in SO ewes but to a lesser degree in AN ewes; FO induced a large and rapid increase in FSH levels in both groups. In conclusion, AN of the ovary to the liver via the mesenteric vein provides a useful model for studying the feedback between the ovary and the hypothalamo-pituitary system and the mechanisms controlling follicle development. The present results indicate that the pattern of LH secretion is an important factor controlling the terminal phase of follicle development in the ewe.

Activins↗
PubMed2000

The bromochlorofluoromethane saga.

Synthesis of optically active samples of bromochlorofluoromethane (CHFClBr) was performed via fractional crystallisation of the strychnine salts of bromochlorofluoroacetic acid (FClBrCCO2H). The S-(+) (R-(-)) absolute configuration of the acid was established by X-ray crystallography and the S-(+) (R-(-)) absolute configuration of the haloform was determined using Raman Optical Activity (ROA) and molecular modelling of the enantioselective molecular recognition process of CHFClBr by the chiral cryptophane-C. From these stereochemical assignments it was observed that the decarboxylation used to obtain S-(+)- and R-(-)-CHFClBr from respectively S-(+)- and R-(-)-FClBrCCO2H occurred with retention of configuration. Finally, the first parity violation (PV) test on CHFClBr was performed and yielded an upper bound for this small stereophysical effect.

Journal Article↗
PubMed1998

Design and synthesis of hydrazinopeptides and their evaluation as human leukocyte elastase inhibitors.

The name hydrazinopeptide designates peptidic structures in which one of the native CONH links is replaced by a CONHNH (hydrazido) fragment. In this paper, we report the synthesis of such hydrazinohexapeptides (3-5) analogous to Z-Ala-Ala-Pro-Val-Ala-Ala-NHiPr (6), a substrate of human leukocyte elastase (HLE; EC 3.4.21.37), cleaved by this serine protease between the Val4 and Ala5 residues. In hydrazinopeptides 3-5, the Ala5, Val4, or Pro3 residue, respectively, of the model peptide, has been replaced by the corresponding alpha-L-hydrazino acid. In 3, the bond likely to be cleaved by HLE is the one involving the CONHNH link, while in 4 and 5, this link is normally shifted away by one or two amino acid units from the catalytic serine. On incubation with HLE, hydrazinopeptide 3 proved to be a substrate and was cleaved between Val4 and NHAla5, like peptide 6. In contrast, 4 and 5 proved to bind to HLE without being cleaved, featuring properties consistent with reversible competitive inhibition. General guidelines for the synthesis of hydrazinopeptides are also reported in this paper. These guidelines take into account the chemical specificity of hydrazino acids, while being fully compatible with the conventional peptide coupling techniques. The utilization of orthogonally bisprotected hydrazino acids 1 where the Nbeta and Nalpha atoms bear a Boc and a Bzl group, respectively, is recommended for the easy construction of such hydrazinopeptides.

Drug Design↗
PubMed1997

Relations between acetylcholine release and electrophysiological characteristics of theta rhythm: a microdialysis study in the urethane-anesthetized rat hippocampus.

In urethane-anesthetized rats, recording electrodes were implanted in the left dorsal hippocampus and a dialysis probe was placed in the contralateral dorsal or ventral hippocampus. Samples of extracellular acetylcholine (ACh) levels were assessed at 10-min intervals over a period of 30 min using microdialysis with high-performance liquid chromatography with electrochemical detection. EEG was recorded during the same period and amplitude, frequency, and duration of theta rhythm were calculated for each of the three 10-min intervals. Data were analyzed using the two-tailed Spearman rank-order correlation test. A positive and high rank correlation coefficient (rho = 0.90, p < 0.01, n = 8) was seen between the average ACh outflow in the dorsal hippocampus and the average theta amplitude, both being calculated for the entire collection period. A lower but statistically significant positive correlation (rho = 0.59, p < 0.01) between dorsal hippocampus ACh output and theta amplitude was also found when the couples of values collected for the 30-min period were pooled (n = 20). In contrast, frequency and duration of theta were not significantly correlated with dorsal hippocampus ACh release. Also, no statistically significant correlation (p > 0.05) was found between ACh output in the ventral hippocampus and theta parameters. Because changes in hippocampal ACh outflow are believed to be the reflection of changes in number and/or level of activity of cholinergic afferents to the dorsal hippocampus, our present findings support the view that, at least in the dorsal hippocampus of the urethane-anesthetized rat, the septohippocampal cholinergic projection regulates the theta amplitude but not frequency. Finally, the possibility that ACh outflow increase and tonic release in the hippocampus is not a sufficient condition to induce and maintain theta in the urethane-anesthetized rat is discussed.

Acetylcholine↗
PubMed1997

Ileocecal segment transposition does not alter whole gut transit in humans.

OBJECTIVES: We have recently described a reservoir for rectal replacement after total mesorectal excision for rectal carcinoma. The ileocecal segment with its intact extrinsic nerve and blood supply is placed between the ascending colon and the anal canal. This reconstruction has been shown to provide good defecation quality and anorectal function. Whether gastric emptying and small as well as large bowel transit are affected by this transposition remains unclear. Our aim was to quantify whole gut transit in such patients and compare it with that of a matched group of controls. METHODS: Gastric emptying rates and small intestinal and colonic transit times were assessed scintigraphically in 12 patients aged 46 to 87 years with ileocecal reservoir reconstruction after total mesorectal excision and compared to a sex-matched group of asymptomatic healthy volunteers of similar age. Gastric emptying rates and small intestinal and colonic transit times were calculated as described previously. Data were compared using Wilcoxon's signed rank test for gastric emptying rates and small bowel transit or by analysis of variance for colonic transit; p < 0.05 was considered significant. RESULTS: Gastric time for half of the meal (T50) was 161 +/- 16 minutes for patients and 201 +/- 22 for the controls. Small bowel transit time was 150 +/- 15 minutes for patients and 177 +/- 22 for the controls. Geometric center at 6 hours was 1.53 +/- 0.13 for patients and 1.27 +/- 0.16 for the controls. Geometric center at 24 hours was 2.96 +/- 0.23 for patients and 2.57 +/- 0.25 for the controls. Data are mean +/- SEM. SUMMARY: Gastric emptying rates and small bowel transit and colonic transit times (expressed as geometric center at 6 and 24 hours) were similar in patients with ileocecal reservoir reconstruction and in a sex- and age-matched group of healthy controls. We conclude that the transposition of an ileocecal segment with intact extrinsic neurovascular supply between the sigmoid colon and the anal canal does not alter whole gut transit, not even in any of the presumably key regions.

Age Factors↗
PubMed1995

Early and transient increase of rat hippocampal blood-brain barrier permeability to amino acids during kainic acid-induced seizures.

The effects of kainic acid (KA) induced seizures on the permeability of hippocampal blood-brain barrier (BBB) to amino acids were investigated using a new method based on the combination of brain microdialysis of alpha-[3H]aminoisobutyric acid (AIB) and blood sampling. The transfer of AIB through the BBB was thus, for the first time, monitored in vivo in awake animals. KA administration i.v. produces a rapid and transient increase in hippocampal transfer of AIB after the beginning of seizures which is closely correlated to epileptic activity. The possible consequences of this increased transport of AIB from blood to brain are discussed in relation to previously reported transient augmentations of extracellular cerebral glutamate concentrations during KA-induced epilepsy.

Amino Acids↗
PubMed1995

[Epidemiology of infantile asthma in the Le Havre region].

BACKGROUND: Prevalence of asthma is influenced by environmental factors which may be different from area to area. POPULATION AND METHODS: A cross-sectional epidemiological survey was carried out among 1,395 children attending primary schools in the city of Le Havre and the canton of Fécamp (Haute-Normandie). Questionnaires including data about the disease, family history, environmental and socio-economic factors were completed by the school physician in presence of the parents. RESULTS: Prevalence rate of asthma calculated from 1,193 questionnaires was 7.8%. The logistic regression curves pointed out four risk factors: family history of asthma (odds ratio: 2.52) or hay fever (OR: 1.98), atopic dermatitis (OR: 3.96), and parental smoking (OR: 1.79). Sex, socioeconomic status of parents, type of housing, presence of pets in the house were not related to prevalence of asthma. Frequency of cough during the day was only significantly different between both areas. CONCLUSIONS: The high level of school absence (21.1%) and frequency of hospitalizations for acute asthma (20.4%) should lead health professionals and educators to improve management of asthma in these areas.

Air Pollution↗
PubMed1994

Synthesis and protease-catalyzed hydrolysis of a novel hydrazinopeptide.

In order to explore the potentiality of hydrazinopeptides as protease inhibitors, the resistance of the hydrazinopeptidic bond toward proteolysis was investigated. To this end, the novel hydrazinohexapeptide Z-Ala2-Pro-Val-hIle-Leu-OMe (1), where hIle represents hydrazinoisoleucine, was designed and synthesized together with the parent peptide Z-Ala2-Pro-Val-Ile-Leu-OMe (2). The interactions of 1 and 2 with human leukocyte elastase (HLE) and porcine pancreatic elastase (PPE) were analyzed comparatively. We observed that 1 behaved as a substrate for both elastases, without the formation of a stable acyl-enzyme as in the case of azapeptides. Compounds 1 and 2 were cleaved at the same site (-Val-parallel-NH-) with a slight delay of hydrolysis for 1 compared to 2 (kcat/KM for 1 vs. 2 decreased by a factor of 2.7 for the HLE-catalyzed hydrolysis at pH 8.0 and 25 degrees C). The presence of the hydrazinopeptide bond (-CONHNH-) in 1 reduced by a factor of 4.7 the apparent enzyme affinity without abolishing it. These results indicate that suitably designed hydrazinopeptides may represent interesting targets in the search for protease resisting pseudopeptides.

Amino Acid Sequence↗
PubMed1994

Crystal structure analysis of a beta-turn mimic in hydrazino peptides.

The crystal structures of four hydrazino peptides (Piv-Pro-h(N alpha-Bzl)Gly-NHiPr 1, Piv-Pro-hAla-NHiPr 2, Moc-hPro-NHiPr 3, and Boc-hPro-Gly-N(OH)Me 4) deriving from the hydrazino analogues of glycine (hGly), L-alanine (hAla) or L-proline (hPro) have been solved. They reveal a common folded structure of the alpha-hydrazino acid residue characterized by a bifurcated hydrogen bond closing an eight-membered cycle. This folded structure is topologically similar to the beta II'-turn in peptides, and the CO-NH-N hydrazide link can be considered as a good turn-inducer in peptide analogues.

Hydrazines↗
PubMed1994

Turn induction by N-aminoproline. Comparison of the Gly-Pro-Gly and Gly psi [CO-NH-N]Pro-Gly sequences.

The folded structure induced by the N-aminoproline residue (the hydrazino analogue of proline, denoted hPro) in the Boc-Gly1-hPro2-Gly3-NHiPr hydrazino tripeptide has been characterized in the solid state by X-ray diffraction, and compared to the usual beta II-turn structure in the Boc-Gly1-Pro2-Gly36-NHiPr cognate tripeptide. It is stabilized by a bifurcated hydrogen bond in which (Gly3)NH interacts with both (Gly1)CO and (hPro2)N alpha. This conformation is retained in CH2Cl2 and CHCl3 solutions, and allows an overall folded conformation of the hydrazino tripeptide in which (iPr)NH is hydrogen-bonded to (Boc)CO. The hPro alpha-hydrazino acid residue appears to promote a local folded structure, and might behave as a beta-turn mimic.

Amino Acid Sequence↗
PubMed1993

Transient impairment of the gabaergic function during initiation of soman-induced seizures.

The changes in extracellular gamma-aminobutyric acid (GABA) levels, the modifications in binding capacities of GABA-receptor subtypes A and B and of the Cl- ionophore sites localized in the ionic-channel associated to the GABAA receptors were studied in hippocampus of rats subjected to a convulsive dose of the acetylcholinesterase inhibitor soman. Whereas extracellular GABA levels, just as binding on GABAA and GABAB receptors, were not modified under soman, a significant transient decrease in the binding capacities of the Cl- ionophore site of the GABAA receptor complex occurred within the first 10 min of seizures in CA1, CA3 areas, and in the dentate gyrus with return to basal values after 30 min. Accordingly, a transient decrease of the brain muscimol-gated Cl- influx was observed after 10 min of seizures. An increased ability of diazepam to potentiate the GABAA gated Cl- influx occurred at the same time. Altogether, these data demonstrated that an impairment of the GABAA receptor function occurs at the beginning of seizures. This suggests that a temporary decrease of GABAAergic function may contribute to the onset of seizures.

Animals↗
PubMed1992

Influence of medial septal cholinoceptive cells on c-Fos-like proteins induced by soman.

The effects of intraseptal application of atropine on c-fos proto-oncogene expression related to soman treatment were studied by immunohistochemistry for c-Fos-like proteins. In control rats, 2 h after the onset of convulsion, c-Fos-like immunoreactivity was intense in the piriform and entorhinal cortices, but also in the cingulate, frontoparietal and retrosplenial cortices. In addition, the staining was moderate in the hypothalamus, amygdala and fascia dentata. The intraseptal application of atropine, which prevented soman-induced convulsions, reduced or even blocked c-Fos-like protein production related to soman treatment. This inhibition of Fos induction was significant in most of the limbic structures but also in non-limbic areas. The data in this study strongly suggest that the cholinergic cells of the medial septal area play a key role in soman-induced seizures, and confirm that c-Fos-like protein induction is closely related to neuronal hyperactivity.

Animals↗