Biomedical subjects

F Robert

Publications and source records attributed to F Robert.

At least 55 records · Page 3Linked to original sources

PubMed1999

UFT/oral calcium folinate plus radiation in pancreatic cancer.

A phase I, single-center, open-label, dose-escalation study (University of Alabama [UAB] 9614) has been undertaken to evaluate the feasibility and safety of uracil and tegafur (in a molar ratio of 4:1 [UFT]) plus oral calcium folinate (Orzel) plus radiotherapy in patients with pancreatic cancer. A total of 11 patients with a median age of 59 years have been treated for 35 days with 150 mg/m2/day of UFT and 90 mg/day of oral calcium folinate, divided into three daily doses. Radiotherapy began on day 1, to a total dose of 45 Gy at 1.8 Gy per day (for approximately 5 weeks). Dose escalation of UFT will be performed until the maximum tolerated dose is defined. Overall, therapy has been well tolerated and the maximum tolerated dose has not yet been reached.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1999

[Neurosteroids: trophic effects in the nervous system].

Some steroids, named "neurosteroïds", can be synthesized from cholesterol within both the central and peripheral nervous systems. Thus, pregnenolone and progesterone persist in the brain and in peripheral nerves long after removal of the steroidogenic endocrine glands by castration and adrenalectomy. The role of neurosteroids during the development of the nervous system is not well known, although they are synthesized by glial cells and some populations of neurons already during embryonic life. Cell culture experiments suggest that neurosteroids may influence the survival and differentiation of neurons and glial cells. In the adult nervous system, neurosteroids play an important role during regeneration. Progesterone is indeed synthesized by Schwann cells in peripheral nerves, where it plays an important role in the formation of new myelin sheaths after lesion. This is the first demonstration of a vital role for a neurosteroid in the nervous system.

Adrenalectomy↗

PubMed1998

Coupling on-line brain microdialysis, precolumn derivatization and capillary electrophoresis for routine minute sampling of O-phosphoethanolamine and excitatory amino acids.

In previous papers, we described the analysis of excitatory amino acids (EAAs) and catecholamines in microdialysis samples using capillary electrophoresis with laser-induced fluorescence detection (CE-LIFD). In the present paper, we report that an automated analysis of such samples can be easily achieved by on-line coupling of the microdialysis probe with a continuous flow derivatization system and a commercially available CE-LIFD apparatus. Because of the short analysis time (less than 2 min) and high separation efficiency (100-200,000 theoretical plates), high temporal resolution of microdialysis (minute range) is preserved as compared to off-line systems, while both EAAs and O-phosphoethanolamine (PEA) can be simultaneously detected. This new method has been applied to the measurement of these compounds in microdialysis samples from hippocampal slice cultures and striatum of anesthetized rats. Extracellular concentrations of EAAs, but not PEA, increased during perfusion of a solution containing high K+ or a glutamate uptake inhibitor. However, after in vitro ischemia on hippocampal slices, both EAAs and PEA concentrations increased, but with different temporal patterns.

Animals↗

PubMed1998

An in vitro blood-brain barrier model: cocultures between endothelial cells and organotypic brain slice cultures.

This communication describes a novel in vitro blood-brain barrier (BBB) model: organotypic slice cultures from the central nervous system were overlaid on endothelial cell monolayers grown on permeable membranes. Morphological, electrophysiological, and microdialysis approaches were carried out to characterize and validate this model. After 10 days in coculture, morphological studies reveal the presence of tight junctions. Electrophysiological recordings of neuronal activity performed on organotypic cultures with or without an endothelial cell monolayer show that amplitude of evoked responses were comparable, indicating good viability of cocultures after 2 weeks. Perfusion of known BBB permeable or nonpermeable molecules was used to test the coculture tightness in conjunction with electrophysiological or microdialysis approaches: application of glutamate (Glu), which doesn't easily cross the BBB, triggers off rhythmic activity only in control cultures, whereas epileptogenic activity was observed in both control cultures and cocultures during perfusions with picrotoxin, a molecule that can diffuse through the BBB. Finally, the microdialysis technique was used to determine the permeability of molecules coming from the perfusion chamber: L-dopa, dopamine, and Glu were employed to assess the selective permeability of the coculture model. Thus, these results indicate that the in vitro model described possesses characteristics similar to those of the BBB in situ and that cocultures of organotypic slices and endothelial cell monolayers have potential as a powerful tool for studying biochemical mechanisms regulating BBB function and drug delivery to the central nervous system.

Animals↗

PubMed1998

Assessment of pharmacodynamic and pharmacokinetic characteristics of drugs using microdialysis sampling and capillary electrophoresis.

Microdialysis sampling combined with capillary electrophoresis is emerging as a new approach in drug studies. It allows the continuous monitoring, in vivo or in vitro, of changes in free endogenous compounds as well as in drug substances, following the administration of pharmacological agents. The low volume requirement of capillary electrophoresis for injection allows the collection of dialysates during short sampling times, leading to a precise temporal description of drug-induced biochemical changes or pharmacokinetics. Various protocols can be used for analyzing endogenous compounds and drug substances in microdialysis samples. Capillary electrophoresis with laser-induced fluorescence detection often affords the high sensitivity level which is needed in most studies. Furthermore, the direct on-line coupling of microdialysis, derivatization of samples, and electrophoretic analysis now brings a separation-based biosensor, allowing a real-time description of chemical events with a high molecular specificity. Microdialysis sampling combined with capillary electrophoresis has recently been used to assess pharmacodynamic and pharmacokinetic characteristics of various drugs in animal studies; it may also represent a new approach in clinical pharmacology in the near future.

Animals↗

PubMed1998

Neurons in primary culture are less efficiently infected by Toxoplasma gondii than glial cells.

Infection by Toxoplasma gondii is asymptomatic, leading to an immune response that controls the disease. In immune-compromised patients, however, quiescent cysts can reactivate, leading to toxoplasmic encephalitis. We studied the infection of cells of the central nervous system in an attempt to understand the process leading to this complication. Primary cultures of rat hippocampal glial cells and neurons were infected with the virulent strain RH and examined by immunofluorescent microscopy after fixation of cells and staining with antibodies specific to the different cell types. After 24 h of infection, glial cells were highly infected and showed active division of the parasite. Neurons, on the other hand, were much less efficiently infected than glial cells, but actual penetration of the parasites was demonstrated by confocal microscopy. Whereas glial cells contained vacuoles with several parasites, the vacuoles observed in neurons usually contained one parasite or, rarely, two, indicating that the parasites inside neurons did not undergo active division. This was corroborated by determination of the incorporation of [3H]-uracil. Little is known about the mechanism of neuronal infection by Toxoplasma. The experimental setup used in this study should help to improve our understanding of neuronal infection and bring insight into the physiopathology of toxoplasmic encephalitis.

Animals↗

PubMed1998

Wrapping of promoter DNA around the RNA polymerase II initiation complex induced by TFIIF.

The formation of the RNA polymerase II (Pol II) initiation complex was analyzed using site-specific protein-DNA photo-cross-linking. We show that the RAP74 subunit of transcription factor (TF) IIF, through its RAP30-binding domain and an adjacent region necessary for the formation of homomeric interactions in vitro, dramatically alters the distribution of RAP30, TFIIE, and Pol II along promoter DNA between positions -40 and +26. This isomerization of the complex, which requires both TFIIF and TFIIE, is accompanied by tight wrapping of the promoter DNA for almost a full turn around Pol II. Addition of TFIIH enhances photo-cross-linking of Pol II to a number of promoter positions, suggesting that TFIIH tightens the DNA wrap around the enzyme. We present a general model to describe transcription initiation.

Adenoviridae↗

PubMed1997

RAP74 induces promoter contacts by RNA polymerase II upstream and downstream of a DNA bend centered on the TATA box.

RAP74, the large subunit of transcription factor IIF, associates with a preinitiation complex containing RNA polymerase II (pol II) and other general initiation factors. We have mapped the location of RAP74 in close proximity to promoter DNA at similar distances both upstream and downstream of a DNA bend centered on the TATA box. Binding of RAP74 induces a conformational change that affects the position of pol II relative to that of the DNA. This reorganization of the preinitiation complex minimally requires the N-terminal region of RAP74 containing both its RAP30-binding domain and another region necessary for accurate transcription in vitro. We propose a role for RAP74 in controlling the topological organization of the pol II preinitiation complex.

Base Sequence↗

PubMed1997

Microdialysis monitoring of extracellular glutamate combined with the simultaneous recording of evoked field potentials in hippocampal organotypic slice cultures.

These experiments combined extracellular electrophysiological multirecordings from hippocampal organotypic slice cultures with application of drugs to and sampling of extracellular fluid from a restricted region of the slice using a microdialysis probe. Glutamate (Glu) concentrations were monitored in 0.5 or 2 min microdialysis samples, while evoked field potentials responses (EvFPR) in the CA1 region of the hippocampus (stimulation in the CA3 area) were simultaneously recorded using a multi-electrodes array (Physiocard). Glu was assayed by capillary electrophoresis with laser-induced fluorescence detection combined with a continuous flow derivatization of dialysates. The performance of this combined approach was demonstrated by monitoring extracellular Glu concentrations and EvFPR after K+ induced depolarisation, Glu uptake blockade by trans-pyrrolidine-2,4-dicarboxylic acid (PDC), and electrical stimulation. Such an approach allows a global monitoring of the neuronal functioning with a fine time resolution (up to 30 s) on a simple in vitro brain slice model, to be used as a complement to conventional in vivo microdialysis studies.

Animals↗

PubMed1997

Monitoring nitric oxide (NO) in rat locus coeruleus: differential effects of NO synthase inhibitors.

A porphyrinic microsensor combined with in vivo voltammetry was used to monitor extracellular nitric oxide (NO) in the locus coeruleus (LC) of anaesthetized rats. Administration of N omega-nitro-L-arginine p-nitro-anilide (100 mg/kg, i.p) or 7-nitro indazole (30 mg/kg, i.p.), which both inhibit preferentially neuronal NO synthase (NOS), induced a marked decrease in the NO oxidation peak height. On the other hand, N omega-nitro-L-arginine methyl ester (L-NAME) (200 mg/kg, i.p.), a less selective NOS inhibitor, failed to decrease the NO signal. Moreover, intra LC administration of NMDA, known to activate LC noradrenergic neurones, increased the NO signal. This study demonstrates the usefulness of in vivo voltammetry to monitor basal levels of NO and their changes in the LC. Differential effects of NOS inhibitors show that their central activity need to be assessed through in situ measurement of NO before using these inhibitors as neuropharmacological tools.

Anilides↗

PubMed1997

Granulocyte-colony stimulating factor (filgrastim) accelerates granulocyte recovery after intensive postremission chemotherapy for acute myeloid leukemia with aziridinyl benzoquinone and mitoxantrone: Cancer and Leukemia Group B study 9022.

This study evaluated the effect of filgrastim (granulocyte colony-stimulating factor [G-CSF]) on the duration of granulocytopenia and thrombocytopenia after intensive consolidation therapy with diaziquone (AZO) and mitroxantrone for patients less than 60 years of age with acute myeloid leukemia (AML) in complete remission. Patients less than 60 years of age with AML who achieved complete remission (CR) with daunorubicin and cytarabine induction therapy, were scheduled to receive three sequential courses of high-dose cytarabine, cyclophosphamide/etoposide, AZQ, and mitroxantrone in a pilot study to determine their tolerance of these three sequential consolidation regimens. The initial patients treated with AZQ and mitroxantrone experienced prolonged bone marrow suppression and, therefore, subsequent cohorts were treated with G-CSF, 5 micrograms/kg, beginning the day after completion of the third cycle of chemotherapy. There was a marked decrease in the duration of granulocytopenia less than 500/microL in two groups of patients receiving two different dose levels of AZQ and the same dose of mitoxantrone compared with patients not receiving the G-CSF. There was also a decrease in the need for hospitalization, as well as the duration of hospitalization. There was a trend towards shortening of the duration of thromobocytopenia, as well. The duration of complete remission and overall survival was similar in patients who received or did not receive G-CSF. G-CSF markedly shortened the duration of granulocytopenia in patients with AML receiving intensive postremission consolidation with AZQ and mitoxantrone. There was no adverse effect on CR duration or survival.

Acute Disease↗

PubMed1997

Brain penetration and neurological effects of gadobenate dimeglumine in the rat.

PURPOSE: The study aimed at measuring the amount of the gadobenate ion that crosses an experimentally disrupted blood-brain barrier (BBB) in rats following i.v. administration of gadobenate dimeglumine (GD). The intention was also to compare this amount with the minimally effective intrathecal dose that alters the cerebral function. METHODS: Sprague Dawley rats with an osmotically disrupted BBB received 0.3 mmol/kg of (153Gd) GD, i.v. Radioactivity was measured in plasma and brain parenchyma. The effect on the cerebral function was evaluated by means of a standard motor coordination test (Rota-rod test). RESULTS: Brain levels of the gadobenate ion were approximately 60 nmol/g tissue after i.v. injection of GD. In rats with an intact BBB, the lowest dose of GD able to slightly impair motor coordination was 0.01 mmol/kg following intracisternal injection. CONCLUSION: I.v. administration of GD to rats with a disrupted BBB results in brain levels of the gadobenate ion that are more than 20 times lower than those reached following intrathecal administration of the minimal effective dose, as determined by the Rota-rod test.

Animals↗

PubMed1997

A phase II study of topotecan in patients with recurrent head and neck cancer. Identification of an active new agent.

This study evaluated the efficacy and safety of topotecan, a topoisomerase I inhibitor, in patients with advanced squamous cell cancer of the head and neck. Topotecan was administered intravenously (over 30 min) daily for 5 days every 3 weeks at a starting dose of 1.5 mg/m2/day. Eligibility required no prior chemotherapy, measurable disease, and performance status of < or = 2. Quality of life (QOL) assessment was performed at specified time points using the Spitzer QOL index and the symptom distress scale. Of 26 patients entered into the study, 23 and 22 patients were assessable for toxicity and response, respectively. One complete and two partial responses were observed, with response durations of 9, 4, and 1.5 months, respectively. Six patients had stable disease, including one patient with a 45% tumor shrinkage. The median survival for all patients entered was 4 months. Neutropenia was the major dose-limiting side effect, with grade 4 toxicity observed in 42% of all cycles of treatment. Grade 3 anemia occurred in 16% of all cycles, and nine patients required blood transfusions. Nonhematologic toxicities were infrequent and mild to moderate. QOL assessment revealed no significant change of total scores between each assessment point. Topotecan is a well-tolerated new agent with similar single-agent activity to that of cisplatin, 5-fluorouracil, and methotrexate in advanced head and neck cancer. Further investigation of this agent with other chemotherapeutic drugs and with concurrent radiation therapy is appropriate.

Adult↗

PubMed1997

Neurosteroids: expression of functional 3beta-hydroxysteroid dehydrogenase by rat sensory neurons and Schwann cells.

Steroids which are synthesized within the nervous system, such as progesterone, have been termed 'neurosteroids'. Levels of progesterone are much larger in peripheral nerves of rats and mice than in plasma, and persist after removal of the steroidogenic endocrine glands. Schwann cells are a source of progesterone: when isolated from embryonic dorsal root ganglia, they can synthesize progesterone from pregnenolone, the obligate precursor of all steroids. Locally produced progesterone has been shown to play an important role in myelination of peripheral nerve. We show here that sensory neurons from embryonic dorsal root ganglia also express 3beta-hydroxysteroid dehydrogenase and can convert [3H]pregnenolone to [3H]progesterone. Moreover, when cultured under different conditions and incubated for 24 h in the presence of 100 nM [3H]pregnenolone, they produce 5-10 times more [3H]progesterone than Schwann cells. The conversion of pregnenolone to progesterone by neurons is further increased by a diffusible factor produced by Schwann cells. Sensory neurons can also metabolize progesterone to 5alpha-dihydroprogesterone, but unlike Schwann cells, they do not produce 3alpha,5alpha-tetrahydroprogesterone, a potent positive allosteric modulator of gamma-aminobutyric acid type A receptors. We also show that cells isolated from the adult nervous system still have the capacity to convert [3H]pregnenolone to progesterone and its 5alpha-reduced metabolites: neurons and Schwann cells purified from dorsal root ganglia of 6 week old male rats show a similar pattern of pregnenolone metabolism to cells isolated from 18 day old embryos. These findings further support the important role of progesterone in the development and regeneration of the peripheral nervous system.

3-Hydroxysteroid Dehydrogenases↗

PubMed1997

Congenital toxoplasmosis due to maternal reinfection during pregnancy.

A case of congenital toxoplasmic chorioretinitis was diagnosed (specific-immunoglobulin G [IgG] and -IgM comparative Western blot analysis) in a baby whose mother was immune during pregnancy. Maternal sera showed an increase in specific IgG and emergence of both IgM and IgA during pregnancy. The mother was probably reinfected through contact with kittens.

Antibodies, Protozoan↗

PubMed1997

Long circulating superparamagnetic particles with high T2 relaxivity.

Novel superparamagnetic particles coated with a phospholipid and a surfactant were characterized and evaluated in vivo. These particles (SBPA) were shown to exhibit r2 relaxivities in the range of 350-450 mM-1.s-1, r1 values of 8-12 mM-1.s-1 and sizes of 50-80 nm. Preliminary results of pharmacokinetics were obtained in rats following the administration of 59Fe-labelled preparations. The particles were shown to remain for hours in the blood stream before being cleared mainly by the liver. Most of 59Fe was eliminated from the body and recovered in the feces within a week. These biodistribution and elimination properties deserve more detailed studies and suggest the potential use of this product as a blood pool contrast agent.

Animals↗

PubMed1996

In vivo monitoring of extracellular noradrenaline and glutamate from rat brain cortex with 2-min microdialysis sampling using capillary electrophoresis with laser-induced fluorescence detection.

The measurement of neurotransmitters by capillary electrophoresis (CE) has emerged as a reliable and sensitive method for microdialysis sample analysis. This paper describes a method which employs laser-induced fluorescence detection (LIFD) of catecholamines and excitatory amino acid derivatives formed after reaction with naphthalene-2,3-dicarboxaldehyde. On-line derivatization of very small volumes of microdialysis samples (500 nl) is developed before two off-line analyses (total run time of less than 10 min) are performed to detect derivatives of catecholamines and excitatory amino acids formed in each sample. High microdialysis temporal resolution is reached (2-min fractions) for the simultaneous monitoring of noradrenaline (NA) and glutamate concentrations from rat brain cortex microdialysates. The system performance is evaluated and pharmacological characterization of the determination of NA in cortical dialysates by CE-LIFD is reported.

Animals↗

PubMed1996

Enhanced temporal resolution for the microdialysis monitoring of catecholamines and excitatory amino acids using capillary electrophoresis with laser-induced fluorescence detection. Analytical developments and in vitro validations.

This paper reports the development of a method based on capillary electrophoresis with laser-induced fluorescence detection for the simultaneous determination of catecholamines and excitatory amino acids on submicroliter microdialysis samples, with short analysis times (3 min or less), high sensitivity (nanomolar range, i.e., attomoles detected) and high separation efficiency (up to 1.10(6) theoretical plates). A continuous flow derivatization of small volumes of microdialysate (500 nl) using naphthalene-2,3-dicarboxaldehyde as derivatizing reagent is described. Thereafter, two subsequent off-line analyses are performed on each of the 30-s dialysates to determine catecholamines and amino acids. The performances of the present method are demonstrated in vitro by monitoring rapid fluctuations in the concentration of catecholamines and amino acids in the external microdialysis medium.

Catecholamines↗