Biomedical subjects

P Thibault

Publications and source records attributed to P Thibault.

At least 73 records · Page 4Linked to original sources

PubMed1998

Development of an on-line preconcentration method for the analysis of pathogenic lipopolysaccharides using capillary electrophoresis-electrospray mass spectrometry. Application to small colony isolates.

The present investigation describes the use of on-line chromatographic preconcentration coupled to capillary zone electrophoresis-electrospray mass spectrometry (cPC-CZE-ES-MS) for trace level analysis of negatively charged lipopolysaccharides (LPS) obtained from pathogenic strains of Haemophilus influenzae. The analytical performance of two different types of adsorption media [i.e., C18 irregular particles and poly(styrene-divinylbenzene) membrane] for anionic analytes was first evaluated using a mixture of peptide standards to determine the overall sensitivity of this approach. These chromatographic preconcentrators provided an enhancement of sample loadings of up to 5 microliters with good linear response and low nM concentration detection limits for most peptides investigated. The application of cPC-CZE-ES-MS is further demonstrated for extracts of O-deacylated LPS obtained from H. influenzae strain Eagan. In combination with novel enzymatic releasing methods using proteinase K, this technique provides unparalleled sensitivity and enabled the identification of LPS surface antigens from as little as five bacterial colonies.

Amino Acid Sequence↗

PubMed1998

Structure of an alpha-2,6-sialylated lipooligosaccharide from Neisseria meningitidis immunotype L1.

The recent cloning of the lipooligosaccharide (LOS) a-2,3-sialyltransferase from Neisseria meningitidis immunotype L3 permitted us to examine other immunotypes for this structural gene. We identified the gene and measured the enzyme activity in the L1 immunotype strain which had previously been reported to lack sialic acid in its LOS because it contains a terminal alpha-linked galactose which was thought not to be an acceptor for the sialyltransferase. This finding prompted us to re-examine the structure of the LOS from the L1 immunotype, which revealed the presence of sialic acid on the terminal alpha-linked galactose. Oligosaccharides derived from the LOS were shown to be sialylated by composition and methylation analysis, mass spectrometry and nuclear magnetic resonance. The detailed structural analysis showed the sialic acid to occur only at 06 of the terminal a-D-galactopyranose residue of the alpha-D-Gal-1,4-beta-D-Gal-1,4-beta-D-glc trisaccharide (Pk epitope) chain of the LOS, in the alpha-D configuration. These data are the first report of a alpha-2,6-linked sialic acid in a bacterial LOS or lipopolysaccharide, and also the first report of a sialylated Pk epitope.

Carbohydrate Conformation↗

PubMed1998

Structural analysis of the phase-variable lipooligosaccharide from Haemophilus somnus strain 738.

The structure of the phase variable lipooligosaccharide (LOS) from Haemophilus somnus strain 738 was elucidated. The LOS was subjected to a variety of degradative procedures. The structures of the purified products were established by monosaccharide and methylation analyses, NMR spectroscopy and mass spectrometry. The following structures for the two major components were determined on the basis of the combined data from these experiments. [structure in text]. In the structures Kdo is 3-deoxy-D-manno-octulosonic acid, PEtn is phosphoethanolamine, PCho is phosphocholine, Hep is L-glycero-D-manno-heptose, and the remaining glucose units have the D configuration. The elucidation of these structures has increased our understanding of the relationship between the phase-variable LOS and the pathogenic potential of this organism.

Haemophilus↗

PubMed1998

Evaluation of adsorption preconcentration/capillary zone electrophoresis/nanoelectrospray mass spectrometry for peptide and glycoprotein analyses.

The use of an on-line adsorption preconcentrator coupled with capillary zone electrophoresis/nanoelectrospray mass spectrometry (PC/CZE/nESMS) is described for the analysis of peptides and protein digests. The investigation was focused on the production of disposable preconcentrators made of large particle size (40 microns irregular packing), thereby eliminating the use of a retaining frit without loss of performance. These preconcentration devices were made of commercially available components which can be easily interfaced to current CZE/nESMS systems. Practical issues such as the composition of the stationary phase, the elution volume and sample breakthrough and carry-over were evaluated in order to optimize the analytical performance of this technique. Under optimized elution conditions, the PC/CZE/nESMS technique provided separation efficiencies in excess of 100,000 theoretical plates for a sample loading of 8 microliters. Sample carry-over was minimized by proper reconditioning of the preconcentrator prior to the CZE separation. Alternatively, the sample carry-over resulting from small elution volumes could be used advantageously to provide multiple analyses from a single injection of sample. The application of this technique is demonstrated for the analysis of proteolytic peptides from a Bauhinia purpurea lectin at a concentration level of 30 nM. Further structural information was obtained using on-line tandem mass spectrometry to elucidate the structure of N-linked glycans and the amino acid sequences of the glycopeptides.

Adsorption↗

PubMed1998

Enhancement of sample loadings for the analysis of oligosaccharides isolated from Pseudomonas aeruginosa using transient isotachophoresis and capillary zone electrophoresis - electrospray - mass spectrometry.

The analysis of underivatized core oligosaccharides arising from mild acid hydrolysis of lipopolysaccharides from Pseudomonas aeruginosa serotype 05 was achieved using a transient isotachophoretic preconcentration method coupled to capillary zone electrophoresis-electrospray-mass spectrometry (tCITP-CZE-ES-MS). The combination of a tCITP preconcentration step provided a 10- to 50-fold enhancement of sample loading and a corresponding improvement in sensitivity compared to the conventional zone electrophoresis format. Electrophoretic conditions, enabling the separation of these anionic analytes, were developed to determine possible sites of heterogeneity on either the core or the O-chain structures. The tCITP-CZE-ES-MS technique provided unparalleled resolution of the different core glycoforms and oligosaccharides obtained from the acid cleavage of the native endotoxins whether isolated following conventional gel permeation chromatography or obtained from direct hydrolysis of the bacterial isolates. These investigations also highlighted the highly phosphorylated nature of these complex cell membrane components, where the heptose residues of the core oligosaccharide can bear up to six phosphate groups.

Carbohydrate Sequence↗

PubMed1998

Intraindividual variability of paracetamol absorption kinetics after a semi-solid meal in healthy volunteers.

OBJECTIVE: The absorption kinetics of paracetamol is dependent on gastric emptying and its measurement was proposed as a non-invasive method to estimate gastric emptying rate. The objective of this study was to evaluate the intraindividual variability of paracetamol absorption kinetics after a semi-solid meal. METHODS: The pharmacokinetics of paracetamol was studied on two occasions in 15 healthy volunteers without Helicobacter pylori antibodies. A 1-g dose of paracetamol was given as a solution together with a standardised semi-solid meal and the subjects stayed in the supine position. RESULTS: For most of the subjects, the time course of paracetamol concentrations was similar on the two occasions. The intraindividual variability was low, with coefficients of variation of 38.3%, 8.0% and 3.8% for time to maximum plasma concentration, maximum concentration and area under the plasma concentration - time curve until 6 h, respectively. CONCLUSION: The assessment of paracetamol absorption kinetics is reproducible when the drug is given together with a semi-solid meal in Helicobacter pylori-negative healthy subjects.

Absorption↗

PubMed1998

Urethral graciloplasty for treatment of female intrinsic sphincter deficiency: rationale for the transvaginal approach: an anatomical study.

PURPOSE: To compare the retropubic and transvaginal approaches in terms of the length of gracilis muscle available for female urethral graciloplasty. MATERIALS AND METHODS: Two groups of female cadavers were submitted to bilateral gracilis muscle dissection, followed by urethral graciloplasty using either the standard retropubic approach or the transvaginal approach. The two groups were studied in terms of various muscle characteristics, in particular the length of muscle that could effectively be wrapped around the bladder neck. RESULTS: Because muscle transfer to the perineum was more direct, the transvaginal approach provided a greater functional length of gracilis for effective periurethral wrapping than the retropubic approach (mean: 8.4 cm. versus 5.2 cm., p = 0.0022). CONCLUSION: The transvaginal approach allows a more "proximal" graciloplasty and should therefore be evaluated clinically to provide circumferential bladder neck support without tension.

Aged↗

PubMed1998

One-week triple therapy using omeprazole, amoxycillin and clarithromycin for the eradication of Helicobacter pylori in patients with non-ulcer dyspepsia: influence of dosage of omeprazole and clarithromycin.

BACKGROUND: Triple therapy based upon omeprazole, amoxycillin and clarithromycin for 7 days is the reference treatment used in France for the eradication of Helicobacter pylori. However, optimal dosages of omeprazole and clarithromycin have not been determined. AIMS: To compare four eradication regimens using this treatment in patients with non-ulcer dyspepsia. METHODS: Two hundred and seventy-four patients with symptoms of dyspepsia, normal upper GI endoscopy and a positive urease test were included in the study. A 13C-urea breath test (UBT) was obtained before and 6 weeks after treatment. Patients were randomized to one of the following 7-day regimens: 20 mg omeprazole o.m. plus amoxycillin 1000 mg b.d. plus clarithromycin 250 mg b.d. (O20AC500) or 20 mg omeprazole o.m. plus amoxycillin 1000 mg b.d. plus clarithromycin 500 mg b.d. (O20AC1000) or 20 mg omeprazole b.d. plus amoxycillin 1000 mg b.d. plus clarithromycin 250 mg b.d. (O40AC500) or 20 mg omeprazole b.d. plus amoxycillin 1000 mg b.d. plus clarithromycin 500 mg b.d. (O40AC1000). Compliance was assessed by returned tablet counts. Eradication was defined as conversion from positive 13C-UBT at entry to negative 13C-UBT 6 weeks after cessation of therapy. RESULTS: Two hundred and fifty-eight patients were included in the intention-to-treat (ITT) analysis. From the least to the most effective regimen, eradication rates were: O20AC1000: 60.0% (95% CI: 47.6-72.4), O20AC500: 64.1% (52.3-75.8), O40AC1000: 64.2% (52.7-75.7), O40AC500: 74.6% (64.2-85.0) (N.S.). Overall compliance was good in 92% of patients. The most frequent adverse events were diarrhoea and taste impairment, occurring mainly in the high-dose clarithromycin groups. CONCLUSIONS: Eradication rates obtained in this study were lower than those expected on the basis of previously reported studies. This study supports the use of a double dose of omeprazole, although the difference between groups was non-significant, but provides no argument in favour of a high dose of clarithromycin.

Amoxicillin↗

PubMed1998

In vivo inaccessibility of somatostatin receptors to 111In-pentreotide in primary renal cell carcinoma.

The presence of somatostatin receptors on human renal cell carcinomas in surgically removed kidneys has been demonstrated by autoradiography. The aim of this study was to detect to in vivo presence of somatostatin receptors in primary renal tumours and their possible metastases before surgery, using 111In-pentreotide scintigraphy. 201Tl was used as a sensitive tumour-seeking agent with blood flow-dependent uptake. Fifteen patients were imaged before surgical removal of the renal tumour. Thirteen tumours were malignant. The large tumours (more than 4 cm in diameter) did not accumulate 111In-pentreotide or 201Tl. In contrast, the single small tumour accumulated both tracers. A scalp skin metastasis was demonstrated in one patient by 201Tl and 111In-pentreotide uptake. In one case, known lung metastases were visualized with both 201Tl and 111In-pentreotide, but the lung metastases of another three patients as well as one case of epidural metastasis were not identified. In one patient with a photopaenic lesion, positive labelling of the surgically removed tumour was demonstrated by in vitro autoradiography. Somatostatin receptor scintigraphy with 111In-pentreotide appears to have little value for the detection of metastases in patients with renal cell carcinoma, as some metastases (especially those of the lungs) were missed. The absence of 111In-pentreotide uptake by large primary tumours is an interesting finding, suggesting inaccessibility of these very large tumours to drugs.

Adult↗

PubMed1997

Structural analysis of the lipopolysaccharide from Vibrio cholerae serotype O22.

The structure of the lipopolysaccharide (LPS) from Vibrio cholerae serogroup O22 was elucidated. The LPS was subjected to a variety of degradative procedures, and the structures of the purified products were established by monosaccharide and methylation analyses, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry. The following structure for the complete LPS molecule was determined on the basis of the combined data from these experiments. [formula: see text] The elucidation of this structure provided a chemical basis for the serological cross-reactions observed between this strain and V. cholerae serogroup O139.

Carbohydrate Conformation↗

PubMed1997

Retroperitoneal laparoscopic nephrectomy of native kidneys in renal transplant recipients.

BACKGROUND: The purpose of this study was to compare retroperitoneal laparoscopic nephrectomy in transplant recipients and in other patients scheduled for nephrectomy. METHODS: From February 1994 to July 1996, 15 transplant recipients and 17 other patients underwent a total of 36 retroperitoneal laparoscopic nephrectomies for various indications. Operative time, morbidity, and hospital stay were compared between the two groups. RESULTS: The average operating time for the 36 procedures was 95+/-38 min (range, 35-180 min). It was shorter in transplant recipients (81+/-32 min) than in other patients (100+/-39 min, P<0.05). There was one postoperative complication in the transplant recipient group. The average length of the postoperative hospitalization was 3.7+/-1.4 days (range, 2-8 days). CONCLUSIONS: The retroperitoneal laparoscopic approach for nephrectomy is as safe and effective in renal transplant recipients as in other patients. Postoperative stay and delay to resumption of oral immunotherapy are short. This approach has become our first-line approach for native nephrectomy in transplant recipients.

Adolescent↗

PubMed1997

Electrospray tandem mass spectrometry of a novel series of amphipathic functionalized ether-linked di- and trisaccharides and cyclic oligosaccharides.

Electrospray mass spectrometry (ESMS) has aided the structural characterization of a novel series of amphipathic functionalized ether-linked di- and trisaccharides, composed of units of alkyl derivatives of glucofuranose and either units of glucofuranose or diacetylgalactose. The structural elucidation of a novel eight-membered macrocyclic ether-linked disaccharide and an 11-membered macrocyclic ether-linked trisaccharide was also effected using ESMS. Low-energy collision-induced dissociation MS/MS analysis of the [M + H]+ precursor ions confirmed the characteristic fingerprint patterns obtained in the conventional electrospray spectra and proved to be a specific and very sensitive method for the detection and characterization of these novel amphipathic molecules.

Disaccharides↗

PubMed1997

Probing the substrate specificity of an enzyme catalyzing inactivation of streptogramin B antibiotics using LC-MS and LC-MS/MS.

LC-MS and LC-MS/MS analyses indicated that an enzyme responsible for inactivating the antibiotic etamycin is specific for streptogramins and acts on both type B-I and B-II streptogramin subgroups. No enzymatic activity was detected for other cyclodepsipeptides such as surfactins and viscosin. It was demonstrated using analogs of etamycin that the picolinyl moiety is essential to obtain enzyme-generated ring-opened compounds. Because the picolinyl moiety is also essential for the biological activity of streptogramins, it is proposed that this residue is a distinctive topographic feature in the binding of this group of antibiotics to enzyme active sites.

Chromatography, Liquid↗

PubMed1997

Analysis of domoic acid and isomers in seafood by capillary electrophoresis.

Methods for the analysis of domoic acid (DA) based upon capillary electrophoresis (CE) combined with UV absorbance detection were investigated. DA could be analyzed using bare fused-silica capillaries in either the cationic or anionic mode with acidic or basic buffer systems, respectively. Highest performance, in terms of both separation efficiency and analysis time, was achieved with phosphate or borate buffers at a pH of approximately 9. The addition of beta-cyclodextrin to the borate buffer permitted a separation of DA and several of its isomers (isodomoic acids) that was superior to that achieved with liquid chromatography (LC). The optimum background electrolyte for the separation was 22.5 mM sodium tetraborate at pH 9.2 with mM beta-cyclodextrin. In addition, an extraction and clean-up procedure was developed and tested with mussels, clams and anchovies. Aqueous methanol extraction of samples followed by a tandem strong anion and strong cation exchange clean-up provided an extract that was completely compatible with CE analysis. A mass detection limit of 3 pg of DA injected and a method detection limit of 150 ng/g in tissues could be achieved. Comparison with LC showed that comparable precision and accuracy could be attained by the two techniques.

Animals↗

PubMed1997

Sulfoquinovosyl diacylglycerols from the alga Heterosigma carterae.

An extract of the chloromonad Heterosigma carterae (Raphidophyceae), cultivated in natural seawater, contained a complex mixture of sulfoquinovosyl diacylglycerols. Palmitoyl (16:0), three isomers of hexadecenoyl (16:1 cis delta 9, delta 11, delta 13), and eicosapentenoyl (20:5) were found to be the main fatty acyl substituents. Exact double-bond sites were determined by mass spectrometry analysis of the corresponding nicotinyl derivatives. Four major sulfoquinovosyl diacylglycerol components were partially purified and identified as 1-4 by interpretation of their nuclear magnetic resonance and mass spectral data. In addition, complete analysis of the H. carterae sulfoquinovosyl diacylglycerols was performed using high-performance liquid chromatography combined with electrospray tandem mass spectrometry.

Diglycerides↗

PubMed1997

Construction and validation of a short-form benign prostatic hypertrophy health-related quality-of-life questionnaire. BPH Group in General Practice.

OBJECTIVE: To construct and validate a short-form benign prostatic hypertrophy (BPH) health-related quality-of-life (HRQL) questionnaire which is more practical in use and as informative as the 20-item visual analogue scale questionnaire (QOL20) previously validated in French. PATIENTS AND METHODS: From the factorial structure of the QOL20, a nine-item questionnaire (QOL9) was constructed using stepwise linear regression and factorial analysis. The feasibility and reliability of the QOL9 were analysed in a cross-sectional case-control study and a longitudinal cohort study, including symptomatic patients with BPH treated for 6 months with an alpha 1-blocker (alfuzosin). RESULTS: The reduction of the QOL20 to QOL9 showed a minimal loss of information (90-95% of the variance of QOL20 was explained by QOL9) and lead to a three-dimensional structure: well being, patients' perceived sexual-life status, and BPH interference with activities. The QOL9 was practical in use (completion rate 87-100%; duration of completion at inclusion 11.6, SD 2.0 min), consistent (Cronbach's alpha > 0.7), reliable (intraclass correlation coefficient > 0.80) and responsive (effect-size index 0.9, SD 0.01 in the longitudinal study). CONCLUSIONS: The QOL9 is a good BPH HRQL questionnaire, including an assessment of patients' perceived sexual-life status; it easy to administer, accurate, reproducible and responsive to change with treatment. We suggest that the QOL9 be substituted for the QOL20 and administered in addition to the International Prostate Symptom Score to obtain a better assessment of the patients' perception of their disease.

Adrenergic alpha-Antagonists↗

PubMed1997

Renal cell carcinoma of native kidneys: prospective study of 129 renal transplant patients.

PURPOSE: We evaluated the prevalence of renal cell carcinoma of the native kidneys in renal transplant recipients as well as possible risk factors. MATERIALS AND METHODS: A total of 129 consecutive renal transplant recipients underwent ultrasound examination of the native kidneys as part of a routine evaluation. A record was made of acquired cystic kidney disease, defined as 3 cysts or more, and of suspicious masses. When a malignancy was suspected radical nephrectomy was performed. RESULTS: The overall prevalence of renal cell carcinoma of the native kidney was 5 in 129 recipients (3.9%). All cancers were limited to the kidney. No significant relationship was detected between renal cell carcinoma occurrence and patient age, dialysis (when initiated, type and duration), transplantation, drug regimen or incidence of acquired cystic kidney disease. CONCLUSIONS: The risk of renal cell carcinoma, a clinically significant cancer, was approximately 100 times greater in our renal transplant patients than in the general population but no significant risk factor could be identified. Routine ultrasonography for early diagnosis in asymptomatic patients on immunosuppressive therapy is strongly recommended to improve prognosis.

Adult↗

PubMed1997

In situ extracorporeal shock wave lithotripsy for acute renal colic due to obstructing ureteral stones.

The purpose of the present study was to evaluate in situ extracorporeal shock wave lithotripsy (ESWL) for the treatment of obstructing ureteral stones causing acute renal colic. In situ ESWL with an EDAP LT-02 piezo-electric lithotriptor was used in a prospective study to treat 67 patients with obstructing ureteral stones causing acute renal colic. Patients were treated without anesthesia on an out-patient basis or during a one-day hospital stay. The overall one month stone-free rate was 94% (94% for proximal stones and 95% for distal stones). The overall success rate after a single ESWL session was 81%. Treatment was well tolerated in 90% (60/67) of patients. There was one case of non-obstructive pyelonephritis and one of ureteral edema. These rates compare well with published reports for delayed treatment in patients without renal colic. Immediate ESWL for cases of acute renal colic due to obstructing ureteral stones is an effective treatment strategy that warrants wider consideration.

Acute Disease↗