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P Thibault

Publications and source records attributed to P Thibault.

At least 109 records · Page 6Linked to original sources
PubMed1995

Mass spectrometric analysis of genetic and post-translational heterogeneity in the lectins Jacalin and Maclura pomifera agglutinin.

Jacalin and M. pomifera agglutinin are T-antigen specific lectins with alpha 4 beta 4 structures that show far greater micro-heterogeneity than plant lectins from other families, due to multiple genetic isoforms and post-translational processing. Electrospray mass spectrometry and combined liquid chromatography-electrospray mass spectrometry were used to characterize the various forms. For both lectins, the mass data were consistent with previous protein sequencing of the major alpha-chain species of 133 residues and three beta-chain species of 20 or 21 residues. In addition, for jacalin the mass of one minor alpha-chain species was consistent with a second of the four reported gene sequences. However, the glycopeptide alpha-chain form and one beta-chain form did not match any of the genes, suggesting a fifth gene remains to be found. For M. pomifera agglutinin, three more beta-chain forms were found, but all six could arise from only two genes, with additional post-translational proteolysis and post-translational substitution with an unidentified component of 106 Da creating the set of six forms. Only two alpha-chain forms were found also, with no glycosylation.

Amino Acid Sequence↗
PubMed1995

Complete amino acid sequence of Proteus mirabilis PR catalase. Occurrence of a methionine sulfone in the close proximity of the active site.

The catalase of Proteus mirabilis PR, a peroxide-resistant (PR) mutant of Proteus mirabilis, binds strongly NADPH, which is a unique property among known bacterial catalases. The enzyme subunit consists of 484 amino acid residues for a mass of 55,647 daltons. The complete amino acid sequence was resolved through the combination of protein sequencing, mass spectrometry, and nucleotide sequencing of a PCR fragment. The sequence obtained was compared with that of other known catalases. Amino acids of the active site are all conserved as well as essential residues involved in NADPH binding. Among the amino acids interacting with the heme, a methionine sulfone was found at position 53, in place of a valine in most other catalases. The origin of oxidation of this methionine is unknown, but the presence of this modification could change iron accessibility by large substrates or inhibitors. This posttranslational modification was also demonstrated in the wild-type P. mirabilis catalase.

Amino Acid Sequence↗
PubMed1995

Improvement of postischemic kidney function by reperfusion with a specifically developed solution (BT01).

Reperfusion is a critical phase of organ preservation. The purpose of this study was to develop a solution specifically for postischemic kidney reperfusion. Unilateral left normothermic kidney ischemia was induced for 60 minutes in two groups of micropigs. In group 1 (control pigs, n = 6) the kidney was reperfused immediately with pure blood at systemic pressure by unclamping the renal artery. In group 2 (test animals, n = 6) the kidney was initially reperfused with an intracellular flush solution enriched with solution BT01 composed of cytoprotectors (natriuretic factor, PGI2), free radical chelating agents (allopurinol, mannitol), and substrates for the mitochondrial respiratory chain (aspartate, glutamate). This solution was mixed immediately before use with blood in a ration of 1:4 parts and injected into the left renal artery with a perfuser at a constant pressure of 60 mm Hg. After 20 minutes, the kidney was reperfused with systemic blood for 100 minutes. Glomerular filtration rate (GFR) was determined by measuring inulin clearance. Kidney blood flow was measured throughout the experiment. After 120 minutes of reperfusion, the kidneys were removed for histologic examination. In the control pigs (group 1) 50% of the animals were anuric. The ratio between GFR measured in the left kidney at the end of perfusion and at equilibrium in the remaining animals was 0.16 +/- 0.01. In test animals (group 2) all animals recovered diuresis. The ratio between GFR measured in the left kidney at the end of perfusion and equilibrium was 0.51 +/- 0.12 (p < 0.001, group 2 vs. group 1). In group 2 postperfusion kidney blood flow was higher than in group 1 (63.0 ml/min vs. 27.4 ml/min; p < 0.05) because of a decrease in renal vascular resistance. Light microscopic examination of kidneys form animals in group 1 revealed tubular necrosis that extended to the parenchyma, with exposure of tubular interstitium. In group 2 only degenerative lesions with edema of tubular cells and disappearance of brush borders were observed. Our findings indicate that flushing the kidneys with BT01 solution mixed with blood improves postischemic kidney function by reducing reperfusion damage.

Animals↗
PubMed1995

Three families of thiol peptides are induced by cadmium in maize.

Phytochelatins ((gamma GluCys)nGly) are synthesized from glutathione by plants exposed to metals like Cd2+, Cu2+ and Zn2+. An intracellular complex formed by phytochelatins with Cd2+ and sulfide is thought to detoxify the metal possibly by sequestration in the vacuole. It was found that maize seedlings exposed to Cd2+ produced phytochelatins and two additional families of cysteine-containing peptides, (gamma GluCys)n and (gamma GluCys)nGlu. All thiol peptides with n = 2 and 3 were purified and their structure characterized by tandem mass spectrometry. For maize plants exposed to Cd2+ for 7 days, phytochelatins were synthesized preferentially in the first 24 h whereas the amounts of (gamma GluCys)n and (gamma GluCys)nGlu were the highest thereafter. This was probably due to an initial large pool of glutathione available in control plants compared with a dearth of gamma GluCys and no detectable gamma GluCysGlu. The (gamma GluCys)nGlu peptides were induced exclusively by Cd2+ as they were below the detection limit in control seedlings that contained low amounts of phytochelatins and (gamma GluCys)n. Since the Cys moiety of the peptides is essential for binding Cd2+, a role for accumulated (gamma GluCys)n and (gamma GluCys)nGlu in detoxifying Cd2+ in plants must be considered.

Amino Acid Sequence↗
PubMed1995

Transrectal and transurethral hyperthermia versus sham treatment in benign prostatic hyperplasia: a double-blind randomized multicentre clinical trial. The French BPH Hyperthermia.

OBJECTIVE: To compare the safety and efficacy of hyperthermia for the treatment of benign prostatic hyperplasia (BPH), by either the transrectal or transurethral approach, relative to sham treatment. PATIENTS AND METHODS: Two hundred patients from seven urological departments were randomized and treated in a single centre. Principal inclusion criteria were a peak flow rate (PFR) < 15 mL/s and residual urine < 300 mL/s. Comparisons were made between transurethral hyperthermia (TUH) and transurethral sham (TUS) and between transrectal hyperthermia (TRH) and transrectal sham (TRS) 12 months after treatment. Outcome was assessed by improvements in the Madsen score and PFR, and the incidence of side-effects. RESULTS: After 12 months, 145 patients were evaluated; 12 patients withdrew during treatment, 43 withdrew during follow-up and two were lost to follow-up. Withdrawals were mainly due to side-effects during treatment (17% in the TRH and 1.5% in the TUH group) and to a lack of improvement during follow-up (14% in the TUH group, 19% in the TUS, 15% in the TRH and 10.5% in the TRS group received other treatments for BPH). Complications during treatment consisted mainly of local pain, urethral bleeding, urethral pain and acute retention, and were five times more frequent in the TRH than the TUH group (34% versus 6%). There was no improvement in PFR after TUH and TRH (response < 20%). Only TUH improved the Madsen score (TUH, +50% and TUS, +17%). CONCLUSION: Hyperthermia was not an effective treatment for BPH.

Aged↗
PubMed1995

[The value of PSA density for the diagnosis of prostatic cancer and for the indication of radical prostatectomy].

We evaluated the diagnostic and prognostic value of PSA density (PSAD) in a prospective study of 100 men consulting for various urinary tract disorders. PSAD was calculated by the ratio of serum PSA over the ultrasonographic volume of the prostate gland, and was expressed in ng/ml/ml. The mean PSAD of 31 patients with prostate cancer was significantly higher than that of the 69 patients without prostate cancer (p = 0.0003). The patients were classified into two groups according to the serum PSA value. Forty nine patients had a serum PSA < or = 10 ng/ml, 31 of whom had a PSAD < or = 0.15 ng/ml/ml and 29 of these 31 patients (94%) did not have prostate cancer; 18 patients had a PSAD > 0.15 ng/ml/ml and six of them (33%) had prostate cancer (p = 0.04). Fifty one patients had a serum PSA > 10 ng/ml and 23 of them (45%) has prostate cancer; 14 of these 51 patients had a PSAD < or = 0.30 ng/ml/ml and two of them (14% à had prostate cancer; 37 patients had a PSAD > 0.30 ng/ml/ml, 21 of whom (57%) had prostate cancer (p = 0.016). Twenty one of these 31 patients with prostate cancer were candidates for radical prostatectomy. Four patients were N+ and 17 underwent radical prostatectomy. Capsular invasion was significantly correlated with PSAD. None of the four patients with PSAD < or = 0.30 ng/ml/ml showed capsular invasion, while 11 of the 13 patients (85%) with PSAD > 0.30 ng/ml/ml had capsular invasion. In conclusion, in patients with PSA < or = 10 ng/ml, calculation of the PSAD avoids approximately two-thirds of prostatic biopsies, with a very low risk of missing a clinically significant cancer. On the other hand, PSAD is of more limited value in patients with PSA > 10 ng/ml. In cancers considered to be operable clinically, the cut-off value of 0.30 ng/ml/ml for PSAD is predictive of capsular or lymph node invasion with a diagnostic accuracy of 94%.

Aged↗
PubMed1995

[Kidney surgery using lumbar endoscopy: initial experiences].

OBJECTIVES: To evaluate the feasibility, safety and clinical value of lumboscopy for the treatment of upper urinary tract diseases. METHODS: Six nephrectomies, one renal biopsy and one renal cystectomy were performed by retroperitoneoscopy (lumboscopy) in 7 patients. These cases represent the beginning of our experience. The operating time, incidence of intraoperative or postoperative complications and length of hospital stay were studied. RESULTS: The mean operating time was 134 min for nephrectomy, 180 min for cystectomy and 30 min for renal biopsy. No complications were observed. No conversion into laparotomy was required. The mean postoperative hospital stay was 3 days in the patients who were submitted to a single operation. CONCLUSION: Lumboscopy is a relatively easy, safe and reliable technique, and its use in urology warrants further study and development. Dissection of the retroperitoneal space with low pressure CO2 is possible and simplifies the procedure, without increasing the risks for the patient. The indications, especially for nephrectomy, are currently under evaluation.

Adult↗
PubMed1994

Development of a capillary electrophoresis method for the characterization of enzymatic products arising from the carbamoylase digestion of paralytic shellfish poisoning toxins.

A sample stacking procedure is presented for the capillary electrophoretic (CE) separation of paralytic shellfish poisoning (PSP) toxins dissolved in high ionic strength buffers. The application of such a stacking procedure prior to the zone electrophoretic separation is demonstrated for the analysis of decarbamoyl toxins arising from the digestion of PSP toxins by an hydrolytic enzyme from little neck clams (Protothaca staminea). Improvements in separation efficiency facilitated identification and quantitation of substrates and enzymatic products present in the digest using CE. The separation conditions developed were found to be entirely compatible with electrospray mass spectrometry, which permitted the analysis of PSP toxins and their decarbamoyl derivatives present in the low micromolar range in crude enzyme digests. The products released during the enzymatic digestion were identified using CE combined with tandem mass spectrometry.

Animals↗
PubMed1994

Purification and properties of a halophilic catalase-peroxidase from Haloarcula marismortui.

A heme protein, hCP, from the extreme halophile, Haloarcula marismortui, showing both peroxidatic and catalatic activity has been purified and characterized as a catalase-peroxidase. Catalatic activity is enhanced by molar concentrations of NaCl or (NH4)2SO4, while peroxidase activity decreases with increasing salt concentration. Optimal pH values are 6.0 for peroxidatic activity assayed in absence of NaCl and 7.5 for catalatic activity assayed in molar concentrations of NaCl. The two activities present saturation behaviour with increasing H2O2 concentration with apparent Km values of 0.5 and 2.5 mM for the peroxidatic and catalatic activities, respectively. A molecular mass of 81,292 +/- 9 Da was measured for the polypeptide by mass spectroscopy. One heme group (protoporphyrin IX with an iron atom in the ferric state) is associated with one molecule of hCP. Its amino-acid composition shows hCP to contain a high proportion of acidic residues. The EPR spectrum of the NO-compound of reduced (ferrous) hCP strongly suggests that the proximal ligand of the heme is the imidazole group of a histidine residue.

Amino Acids↗
PubMed1994

Isolation and purification procedures for the preparation of paralytic shellfish poisoning toxin standards.

Paralytic shellfish poisoning (PSP) is caused by mixtures of saxitoxin analogs of which more than eighteen are known. Reliable and sensitive analytical methods and assays for these toxins are essential to protect the consumer and the shellfish industry, but research has been restricted by a shortage of the pure compounds. Only saxitoxin has so far been generally available as a PSP toxin standard, yet sulfated analogs usually occur in higher concentrations than saxitoxin in toxic marine algae and shellfish. Methods are described for the purification of some of the common PSP toxins, in quantities sufficient for the preparation of PSP standards from the dinoflagellate Alexandrium excavatum, the giant sea scallop (Placopecten megallanicus) hepatopancreas, and the cyanobacterium Aphanizomenon flos-aquae. Purity was monitored by high performance liquid chromatography with fluorescence detection (HPLC-FD), ionspray mass spectrometry (ISP-MS), capillary electrophoresis (CE), and proton NMR spectroscopy.

Animals↗
PubMed1994

Laparoscopic pelvic lymph node dissection for staging of prostatic cancer.

Assessment of the pelvic lymph node status is a major concern in prostatic cancer staging. In spite of a normal abdominopelvic CT scan examination in patients with organ-confined disease, 7-30% will have lymph node metastases at pathological examination and will not benefit from radical prostatectomy. Laparoscopy enables pelvic lymph node dissection via a minimally invasive approach. Twenty-nine patients underwent laparoscopic pelvic lymph node dissection (LPLND) for prostatic cancer staging. The average duration of the bilateral dissection was 90 +/- 40 min (range 35-180 min). One patient died of a stroke on postoperative day 1, without local complication. The peroperative complications were 1 injury of the external iliac vein, 1 ileal injury, 1 ureteral injury, all 3 (11%) requiring immediate or delayed laparotomy. One patient had a self-resolving bilateral obturator nerve paresis. A previously irradiated patient had perineal lymphedema for 4 weeks. The average number of lymph nodes removed was 8.4 +/- 3.4 (range 4-17) for bilateral LPLND. Five patients had lymph node metastases. The median length of stay for patients undergoing LPLND as a single procedure was 2 days (range 2-11 days). After an operational period, during which the complication rate was relatively high, we now consider LPLND as a safe and effective procedure for the staging of patients with organ-confined prostatic cancer, but considering the increased risk of complications during the application period, we do not encourage the generalization of this technique which should remain restricted to some particular strategies, as in combination with perineal radical prostatectomy.

Aged↗
PubMed1994

[Urethro-vesical stenosis after radical prostatectomy].

Stricture of the urethrovesical anastomosis is an uncommon complication of radical prostatectomy, but it can affect the patient's quality of life. From January 1991 to December 1993, 50 patients underwent radical prostatectomy for clinically localised prostatic cancer (41 via a retropubic incision and 9 via a perineal incision). We retrospectively studied the influence of several factors on the incidence of anastomotic stricture: history of prostatic surgery, surgical incision, blood loss, pathological stage, presence of a contrast agent leak during follow-up urethrocystography, postoperative adjuvant treatment, oncological status at the time of the stricture. Seven patients developed clinically significant anastomotic stricture (14%). The time to onset was 1.5 to 10 months (median: 3 months). We were unable to demonstrate any pre-, intra- or postoperative or histological factors able to predict the development of anastomotic stricture. The transperineal approach appears to be associated with a lower incidence, but this finding must be confirmed in a larger series of patients. The seven patients with an anastomotic stricture were treated by endoscopic scalpel incision of the stricture, followed by insertion of a 22 F Foley catheter for 48 hours. No patient has developed a recurrent stricture with a mean follow-up of 8 months (0 to 13 months). Postoperative continence was normal in every case.

Aged↗
PubMed1994

[Radical prostatectomy: comparison of the perineal and retropubic route (40 patients). Preliminary results].

Transperineal radical prostatectomy, described at the beginning of the century for the treatment of prostatic cancer, is currently being reappraised following the development of surgical techniques allowing the dissection of subvenous external iliac nodes via a limited incision. Twenty four patients (group 1) underwent transperineal prostatectomy and 16 (group 2) underwent retropubic prostatectomy. The choice of surgical approach was left to the operator. We retrospectively compared the two groups. All patients had histologically proven prostatic cancer, clinically confined to the prostate. The operating time, the development of complications. the preoperative-postoperative haemoglobin difference, the number of patients transfused and the number of units transfused, urinary continence at three months and the histological results were studied. Three patients operated via the perineal approach and one patient operated via the retropubic approach suffered an operative rectal injury. The number of transfused patients (12.5% in group 1 and 37.5% in group 2) and the preoperative-postoperative haemoglobin difference for non-transfused patients (mean of 2.9 g/100 ml in group 1 vs 4.6 g/100 ml in group 2) were significantly different. No significant difference was observed between the two groups in terms of invasion of the prostatic capsule or seminal vesicles. Overall, only 106 out of 40 patients had a truly intraprostatic tumour, corresponding to understaging of the cancer in 60% of cases. Although the number of patients with imperfect continence was higher in group 1, the difference observed was not significant. The transperineal approach allows prostatectomy to be performed under similar oncological conditions to those of retropubic prostatectomy, while decreasing the operative blood loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

gamma-Glutamylcysteinylglutamic acid--a new homologue of glutathione in maize seedlings exposed to cadmium.

Exposure of plants to Cd induces the appearance of several thiols based on glutathione and known as class III metallothioneins (or phytochelatins). A new tripeptide with the structure gamma-GluCysGlu accumulated in roots and shoots of Cd-exposed maize seedlings. This thiol was purified and identified by tandem mass spectrometry. The fragmentation pattern of the maize tripeptide was identical to that of the synthetic compound. Like glutathione, this new tripeptide may serve as a precursor for longer-chain peptides involved in metal detoxification through the formation of Cd-binding complexes.

Amino Acid Sequence↗
PubMed1993

Fragmentation reactions of multiply-protonated peptides and implications for sequencing by tandem mass spectrometry with low-energy collision-induced dissociation.

The low-energy collision-induced dissociation reactions of a series of multiply-protonated peptides have been investigated by tandem mass spectrometry. It is known that doubly-protonated tryptic peptides undergo facile fragmentation yielding redundant sequence information. The present work has shown that this fortunate circumstance seems likely to be the exception rather than the rule. The presence of additional basic residues, at positions other than the C-terminus, complicates the spectra. The most important such complication discovered in the present work involves wholesale transfer of one or two residues from the C-terminal end of a doubly-charged b fragment to the side chain of a lysine residue located near the N-terminus, resulting in mass shifts of the products of subsequent second-stage fragmentations. Other examples of the participation of the flexible lysine side chain are suggested but could not be confirmed to the same extent. The role of Coulombic repulsion in facilitating fragmentation has been explored via investigations of triply- and quadruply-protonated basic peptides bearing one charge for every three or four amino acid residues. Such species yielded almost no sequence information under low-energy collision conditions, due to the localization of the ionizing protons on highly basic sites rather than on the peptide backbone. It is proposed that collisionally activated mobilization of protons from the basic sites, where they are originally located upon formation, to the backbone is a necessary condition for structurally useful fragmentation to occur. It was not possible, on the basis of the present work, to deduce mechanistic generalizations and predictive schemes which would permit structural interpretations of such fragment spectra for unknown peptides.

Amino Acid Sequence↗
PubMed1993

Characterization of the primary structure of H-protein from Pisum sativum and location of a lipoic acid residue by combined liquid chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry.

A purified extract of H-protein, a subunit of the glycine cleavage complex of the pea leaf mitochondria, was investigated by liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS), using both continuous flow fast atom bombardment (CF-FAB) and electrospray ionization (ESI) mass spectrometry. Determination of the molecular weight of the entire protein, a 14 kDa subunit of the glycine decarboxylase complex, was achieved by ESI mass spectrometry and revealed covalent binding of the protein to the stabilizing agent beta-mercapto-ethanol. On-line LC/MS analysis of peptides arising from the endoproteinase Glu-C digestion of the H-protein was achieved using capillary columns (0.25 mm i.d.), and permitted confirmation of the previously reported sequence deduced from cDNA cloning experiments. The detailed interpretation of data extracted from these LC/MS experiments facilitated identification of peptides containing modified amino acid residues. In particular the identification of a lipoic acid cofactor, a rather unusual modified lysine residue which interacts with different active sites in the enzyme complex, was achieved using both LC/CF-FAB-MS and LC/ESI-MS. The exact location of this modified lysine residue was determined by obtaining fragment spectra of multiply protonated precursor ions of selected peptides, using on-line LC/MS/MS techniques.

Amino Acid Oxidoreductases↗