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B Pirotte

Publications and source records attributed to B Pirotte.

At least 37 records · Page 2Linked to original sources
PubMed2000

Combined magnetic resonance imaging- and positron emission tomography-guided stereotactic biopsy in brainstem mass lesions: diagnostic yield in a series of 30 patients.

OBJECT: In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET) scanning, and histological studies obtained in 30 patients who underwent MR imaging- and PET-guided stereotactic biopsy procedures for a brainstem mass lesion. METHODS: Between July 1991 and December 1998, 30 patients harboring brainstem mass lesions underwent a stereotactic procedure in which combined MR imaging and PET scanning guidance were used. Positron emission tomography scanning was performed using [18F]fluorodeoxyglucose in 16 patients, methionine in two patients, and both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only was in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. Treatment based on information derived from MR imaging was concordant with therapy based on histological findings in only 17 patients (57%). Combining MR imaging and PET scanning data, the concordance between the neuroimaging-based treatment and treatments based on histological findings increased to 19 patients (63%). In seven patients who underwent biopsy procedures with one PET-defined and one MR imaging-defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging-guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases. CONCLUSIONS: Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combining information provided by MR imaging and PET scanning in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the biopsy sample; an MR imaging- and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.

Adolescent↗
PubMed1999

6-Substituted 2-oxo-2H-1-benzopyran-3-carboxylic acid as a core structure for specific inhibitors of human leukocyte elastase.

Pyridyl esters of 6-substituted 2-oxo-2H-1-benzopyran-3-carboxylic acid were designed as mechanism-based inhibitors of human leukocyte elastase. Compounds of series 4 specifically inhibited this enzyme. Several of the tested compounds (series 2 and 3) acted as powerful time-dependent inhibitors of both human leukocyte elastase and alpha-chymotrypsin; some compounds of these series inhibited thrombin. Trypsin was not inhibited. A transient inactivation was observed for human leukocyte elastase (k(i)/K(I) = 107 000 M(-1). s(-1) for 4c) and thrombin (k(i)/K(I) = 7 200 M(-1).s(-1) for 3b) as demonstrated by spontaneous or hydroxylamine-accelerated reactivation, irrespective of the nature of the substituent at the 6-position. Conversely, alpha-chymotrypsin was irreversibly inhibited by 6-chloromethyl derivatives (k(i)/K(I) = 107 400 M(-1). s(-1) for 3b). The presence of a latent alkylating function at the 6-position (chloromethyl group) was required for leading to this inactivation. In the absence of such an alkylating function (series 4), human leukocyte elastase was specifically inhibited suggesting that this new series of human leukocyte elastase inhibitors may be of potential therapeutic interest in degradative and degenerative processes involving this enzyme.

Chromatography, High Pressure Liquid↗
PubMed1999

Preparation and pharmacological evaluation of the R- and S-enantiomers of 3-(2-butylamino)-4H- and 3-(3-methyl-2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide, two tissue selective ATP-sensitive potassium channel openers.

The preparation and the pharmacological evaluation of the R- and S-isomers of 3-(2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide (BPDZ 42) and 3-(3-methyl-2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide (BPDZ 44), two potassium channel openers, is described. Their optical purity was estimated by means of capillary electrophoresis (R- and S-BPDZ 42) and chiral HPLC (R- and S-BPDZ 44). The absolute configuration of each isomer of BPDZ 44 was deduced from crystallographic data. Pharmacological assays performed with the R- and S-isomers of BPDZ 44 revealed only slight differences in their activity on pancreatic B-cells but significant differences in their activity on vascular smooth muscle cells: the R-isomer being sixfold more potent than its corresponding S-isomer. The R-isomer of BPDZ 42 was shown to be more potent than its corresponding S-isomer on the endocrine pancreas. S-BPDZ 44 as well as R- and S-BPDZ 42 were found to exhibit tissue selectivity for the pancreatic versus the vascular smooth muscle tissue.

Adenosine Triphosphate↗
PubMed1999

Prevention of epidural fibrosis in a prospective series of 100 primary lumbo-sacral discectomy patients: follow-up and assessment at re-operation.

An implantable device (ADCON-L), which acts as a resorbable barrier to epidural fibrosis following lumbar discectomy, has been shown to minimize the formation of peridural fibrotic scar and to improve the post-operative outcome, in two large controlled and multi-center clinical trials. In this prospective study, 100 patients were treated with the device during their first-time lumbo-sacral discectomy surgeries and monitored for 12 months. During this time interval, four of these patients required re-operation. In these cases, epidural scar and ease of dissection were systematically evaluated and recorded. At the time of re-operation, in all four patients, absent or minimal soft scar tissue was found where ADCON-L had been placed, no adhesions to the involved root were observed, and the dissection was easier than expected; the healing of the surgical wound was excellent , and no residual implant material was found. These observations indicate that the use of ADCON-L at the time of the first lumbar disc surgery minimizes the hazards and difficulty that can be encountered in a subsequent revision surgery due to the presence of epidural fibrosis, and may therefore improve the chances of satisfactory outcome following re-operation.

Adolescent↗
PubMed1999

Recent advances in the chemistry of cholecystokinin receptor ligands (agonists and antagonists).

During the last few years, cholecystokinin (CCK) has emerged as an important hormone. This polypeptide has been located either in peripheral tissues such as the gastro-intestinal tract and the pancreas as well as in the central nervous system. High affinity CCK receptors are divided in two main subtypes: the CCK-A (A for (A for "alimentary") and the CCK-B (B for "brain") receptors. The latters are currently associated with the gastrin receptors. Since CCK is involved in many different biological processes such as gut function, digestive processes, control of feeding behaviour and neurotransmitter release, the therapeutical potential of cholecystokinin receptor ligands seems to be extremely broad and promising. Several families of CCK receptor ligands (peptides, peptidomimetics, peptoids or non-peptides) were prepared during the last twenty years. The main goal of these researches was to improve agonistic or antagonistic potency but also to find selective compounds for a specific CCK receptor subtype. This review presents the recent developments (since 1995) in the chemistry of CCK receptor ligands.

Animals↗
PubMed1998

4H-1,2,4-Pyridothiadiazine 1,1-dioxides and 2,3-dihydro-4H-1,2, 4-pyridothiadiazine 1,1-dioxides chemically related to diazoxide and cyclothiazide as powerful positive allosteric modulators of (R/S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid receptors: design, synthesis, pharmacology, and structure-activity relationships.

A series of 4H-1,2,4-pyridothiadiazine 1,1-dioxides and 2, 3-dihydro-4H-1,2,4-pyridothiadiazine 1,1-dioxides bearing various alkyl and aryl substituents on the 2-, 3-, and 4-positions was synthesized and tested as possible positive allosteric modulators of the (R/S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors. Many compounds were found to be more potent than the reference compounds diazoxide and aniracetam as potentiators of the AMPA current in rat cortex mRNA-injected Xenopus oocytes. The most active compound, 4-ethyl-2,3-dihydro-4H-pyrido[3,2-e]-1,2, 4-thiadiazine 1,1-dioxide (31b), revealed an in vitro activity on Xenopus oocytes not far from that of cyclothiazide, the most potent allosteric modulator of AMPA receptors reported to date. Moreover, 31b, but not cyclothiazide, was found to potentiate the duration and the amplitude of the excitatory postsynaptic field potentials induced by electric stimulation in rat hippocampal slices. Such an effect could indicate, for 31b, but not for cyclothiazide, a possible interaction with postsynaptic AMPA receptor binding sites located on hippocampal CA1 neurons. Structure-activity relationships indicated that the structural requirements responsible for a biological activity on AMPA receptors are different from those responsible for an inhibitory activity on the insulin releasing process (putative ATP-sensitive K+-channel openers). For instance, 31b and other related dihydropyridothiadiazines were found to be ineffective as inhibitors of insulin release from rat pancreatic B-cells, in contrast to diazoxide and known pyridothiadiazines reported as ATP-sensitive K+-channel openers. Conversely, the pyridothiadiazines active on B-cells were found to be ineffective as potentiators of the AMPA currents in Xenopus oocytes. Thus, 31b appeared to be more specific than diazoxide as an AMPA receptor modulator. This compound may be considered as a new pharmacological tool, different from diazoxide and cyclothiazide, for studying AMPA receptors. Moreover, 31b can also constitute a new therapeutic agent for the treatment of cognitive disorders.

Adenosine Triphosphate↗
PubMed1998

Pyridothiadiazinedioxides structurally related to quinazolinones cholecystokinin/gastrin receptor ligands: synthesis and biological evaluation.

The synthesis of 3-aralkyl-4-aryl-4H-, 3-aralkylamino-4-aryl-4H- and 3-aralkylsulfanyl-4-aryl-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1, 1-dioxides is described. Moreover, the affinity of the different compounds towards the cholecystokinin CCK-A and CCK-B receptors was evaluated. For selected compounds, affinity on the two receptor subtypes was expressed in the micromolar range. This was comparable to the affinity observed with the naturally occurring CCK receptor antagonist asperlicin.

Animals↗
PubMed1998

Lower clivus and foramen magnum anterolateral meningiomas: surgical strategy.

Lower clivus and anterolateral foramen magnum meningiomas are rare but challenging tumors. Indeed, all access routes to their intradural anterolateral implantation appear unsafe since highly-functional local structures may not be sacrified or even retracted. Anterior and posterior surgical approaches have specific advantages and limitations. Different lateral extensions of the posterior approach have been described. They include a transposition of the vertebral artery, a partial occipital condylectomy and even the exposure and the section of the sigmoid sinus. Such posterolateral approaches offer the optimal access to anterolateral foramen magnum meningiomas and allow a total removal with a minimal morbidity. We report the surgical strategy that we applied for the last 6 anterolateral foramen magnum meningiomas in our department.

Aged↗
PubMed1998

Diagnostic and microsurgical presentation of intracranial angiolipomas. Case report and review of the literature.

Angiolipomas (ALs) are hamartomas composed of abnormally differentiated vessels and mature adipose tissue. Although they are most commonly found in peripheral tissues, ALs sometimes grow in the spinal epidural space. Intracranial ALs (ICALs) are rare: only seven cases have been reported in the literature. The authors describe the case of a 70-year-old woman who presented with ocular symptoms from a clinically and radiologically progressing parasellar ICAL. The radiological as well as the microsurgical findings are illustrated and compared with the seven previously published cases. The most frequent location of ALs is the skull base, especially the parasellar region. Other ICALs were diagnosed as components of cerebral arteriovenous malformations and were not symptomatic by themselves. Neuroradiological studies of ICALs usually demonstrate the characteristics of both adipose and vascular tissues. However, a review of the literature shows that the diagnosis had not been suspected preoperatively in any of the cases. Operative descriptions emphasize that most neurosurgeons were caught off guard by the profuse bleeding and the unusual relationship of this unexpected lesion to the cavernous sinus, so that removal was rarely complete. The authors conclude that preoperative diagnosis of ICALs is achievable based on magnetic resonance analysis, which should help optimize the microsurgical management of these lesions.

Aged↗
PubMed1997

Stereotactic brain biopsy guided by positron emission tomography (PET) with [F-18]fluorodeoxyglucose and [C-11]methionine.

The aim of the present study was to compare the contribution of the labelled tracers [C-11]methionine (Met) and [F-18]-fluorodeoxyglucose (FDG) in positron emission tomography (PET)-guided stereotactic biopsy of non resectable brain lesions. Twenty-five patients underwent combined Met-PET-, FDG-PET- and computerized tomography (CT)- or magnetic resonance (MR)-guided stereotactic biopsy according to a previously described technique for stereotactic FDG-PET. Met-PET and FDG-PET images were analyzed to determine which tracer offers the best information to guide at least one stereotactic biopsy trajectory. Histological diagnosis was obtained in all patients (23 tumours and 2 non-tumorous lesions). All tumours had an area of abnormal Met uptake and were biopsied under PET-guidance. FDG uptake in the tumour was higher than in the grey matter and was used for target selection in 12 of 23 tumours. Eleven of them were located in the basal ganglia or the brainstem. Met was used for target selection in 11 of 23 tumours where there was no FDG uptake or where FDG uptake was equivalent to that of the grey matter. Ten of them were located in the cortex. Two nontumoral lesions had no Met uptake and were biopsied under CT- or MR-guidance only. Forty-three out of 53 stereotactic trajectories obtained in these 25 patients were based on PET-defined targets and had an area of abnormal Met uptake. These trajectories always yielded a diagnosis of tumour. Moreover, all tumorous trajectories had an area of abnormal Met uptake. Finally, all non-diagnostic trajectories (n = 4) were CT/MR-defined because there was no area of abnormal Met uptake. These results suggest that patients who can benefit the most from Met-PET guidance could be selected pre-operatively. In conclusion, this work shows that Met is a good alternative to FDG for target selection in PET-guided stereotactic brain biopsy.

Adolescent↗
PubMed1997

Verapamil, a phenylalkylamine Ca2+ channel blocker, inhibits ATP-sensitive K+ channels in insulin-secreting cells from rats.

Radioisotopic and electrophysiological techniques were used to assess the effects of verapamil, a phenylalkylamine Ca2+ channel blocker, on K+ permeability of insulin-secreting cells. Verapamil provoked a concentration-dependent inhibition of 86Rb (42K substitute) outflow from prelabelled and perifused rat pancreatic islets. This property appears to be inherent to the phenylalkylamine Ca2+ channel blockers since gallopamil, a methoxyderivative of verapamil, but not nifedipine, a 1,4-dihydropyridine Ca2+ channel blocker, inhibited 86Rb outflow. The experimental data further revealed that verapamil interacted with a Ca2+-independent, glucose- and glibenclamide-sensitive modality of 86Rb extrusion. Moreover, verapamil prevented the increase in 86Rb outflow brought about by BPDZ 44; a potent activator of the ATP-sensitive K+ channel. Single-channel current recordings by the patch clamp technique confirmed that verapamil elicited a dose-dependent inhibition of the ATP-dependent K+ channel. Lastly, under experimental conditions in which verapamil clearly inhibited the ATP-sensitive K+ channels, the drug did not affect 45Ca outflow, the cytosolic free Ca2+ concentration or insulin release. It is concluded that the Ca2+ entry blocker verapamil inhibits ATP-sensitive K+ channels in pancreatic beta cells. This effect was not associated with stimulation of insulin release.

Adenosine Triphosphate↗
PubMed1997

An atypical infectious complication of anterior cervical surgery.

We report a 44-year-old woman who developed an atypical retro-oesophageal abscess 4 years after anterior cervical surgery with fusion (ACSF). She presented with dysphagia but no fever or definite laboratory signs of inflammation. Delayed or chronic dysphagia following Cloward's operation is usually related to graft displacement. Infection may also, more rarely, be encountered in conjunction with dysphagia, but is typically associated with a classical clinical presentation and laboratory results. We recommend that in cases of delayed dysphagia without evidence of graft migration, the possibility of retropharyngeal infection should be considered, even in the absence of clinical signs or supporting laboratory evidence. MRI in this rare delayed complication is nonspecific but suggestive, and hence represents the imaging modality of choice in such situations.

Adult↗
PubMed1997

Study of the influence of both cyclodextrins and L-lysine on the aqueous solubility of nimesulide; isolation and characterization of nimesulide-L-lysine-cyclodextrin complexes.

Nimesulide is a nonsteroidal antiinflammatory drug that exhibits a very poor water solubility (0.01 mg.mL-1). A nimesulide-beta-cyclodextrin complex prepared according to patent application WO 94/ 02177 has an aqueous solubility of approximately 16 mg.mL-1 of nimesulide. A nimesulide-L-lysine salt has also been prepared and increases the aqueous solubility of nimesulide to approximately 5.0-7.5 mg.mL-1. The purpose of the present study was to investigate the interaction of both cyclodextrins and L-lysine on the aqueous solubility of nimesulide. Nimesulide-L-lysine-beta- or gamma-cyclodextrin complexes were prepared by spray-drying. The inclusion of the nimesulide-L-lysine salt into the cyclodextrin cavity was confirmed by differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy. These complexes offered remarkable aqueous solubility. The incorporation of nimesulide in a nimesulide-L-lysine-beta-cyclodextrin complex increased its water solubility by a factor of 10 at pH 1.5 (0.050 mg.mL-1 for the complex versus 0.005 mg.mL-1 for nimesulide), 160 at pH 6.8 (2.373 mg.mL-1 for the complex versus 0.015 mg.mL-1 for nimesulide), and 3600 in purified water (36.400 mg.mL-1 for the complex versus 0.01 mg.mL-1 for nimesulide).

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Glucocorticoid-induced long-term remission in primary cerebral lymphoma: case report and review of the literature.

We report a 25-year old immunocompetent woman with a high grade primary non-Hodgkin's lymphoma of the central nervous system (PNHL-CNS) in whom the administration of dexamethasone alone during three months produced a complete clinical and radiological response lasting over four years. If complete remission of PNHL-CNS induced by glucocorticoids are well known, the opportunity to observe glucocorticoid-induced remission for a long period of time without radio- and chemotherapy is rare. Only nine other cases of PNHL-CNS with complete remission induced by glucocorticoids lasting from 6 to 60 months, were found in the literature and are summarized here. Duration of glucocorticoids therapeutic effect in PNHL-CNS is probably underestimated. Glucocorticoids cannot be recommended as sole initial treatment for PNHL-CNS. However, we suggest standard therapies to be delayed in those patients responding completely to glucocorticoids where radio- and chemotherapy should be contraindicated (kidney, liver, bone marrow failure, pregnancy).

Adult↗
PubMed1997

Effect of activators and inhibitors of K+ channels on insulin secretion in the amphibian pancreas.

The aim of this study was to obtain pharmacological evidence for the presence and participation of K+ channels in amphibian pancreatic islets. Pancreases from the toad Bufo arenarum were thus incubated with activators or blockers of K+ channels and the immunoreactive insulin released into the medium was measured by radioimmunoassay. Two K(+)-ATP channel openers (diazoxide and BPDZ44) inhibited; while a K(+)-ATP channel blocker (tolbutamide) and metabolizable sugars (glucose, glyceraldehyde) significantly stimulated the output of insulin. Although a nonmetabolizable sugar (galactose) failed to increase insulin release, dinitrophenol decreased the secretagogue effect of glucose. By contrast, although somatostatin and clonidine blocked the release of insulin, tetraethylammonium significantly stimulated secretion. For each compound tested, the effects on both insulin secretion and B-cell K+ channel activity were similar to those observed in the mammalian pancreas. These findings point to the existence of mammalian-like K+ channels in the B-cells of some amphibians.

Animals↗
PubMed1997

Effect of potassium channel openers on the firing rate of hippocampal pyramidal cells and A10 dopaminergic neurons in vitro.

The effect of four KATP channel openers (KCOs) on the firing rate of CA1 pyramidal cells and A10 dopaminergic neurons was investigated using extracellular recording techniques in rat brain slices. Pinacidil, lemakalim, diazoxide and a new compound, BPDZ44, had an inhibitory effect on the electrical activity of CA1 pyramidal cells. They all had a similar potency. Only BPDZ44 and diazoxide inhibited the firing rate of A10 dopamine neurons. The sulfonylurea glipizide (1 microM) antagonized the effect of BPDZ44 and diazoxide on A10 neurons but failed to antagonize the effect of KCOs on CA1 pyramidal cells. These results show that differences exist among KCOs in their ability to decrease the electrical activity of various populations of central neurons.

Action Potentials↗