Biomedical subjects

P Grellier

Publications and source records attributed to P Grellier.

At least 37 records · Page 2Linked to original sources

PubMed2000

Cloning of Plasmodium falciparum protein disulfide isomerase homologue by affinity purification using the antiplasmodial inhibitor 1,4-bis[3-[N-(cyclohexyl methyl)amino]propyl]piperazine..

A series of 10 1,4-bis(3-aminopropyl)piperazine compounds was found to display antiplasmodial activity with 50% growth inhibition between 30 and 250 nM, on three Plasmodium falciparum strains differently sensitive to chloroquine. By affinity chromatography using one of these compounds, a 52-kDa protein was isolated from P. falciparum, microsequenced and cloned. It corresponded to a single copy gene encoding a 453 amino acid protein displaying the typical features of protein disulfide isomerases, a thiol metabolizing enzyme belonging to the thiol: disulfide oxidoreductase superfamily, which was not previously described in malarial species.

Amino Acid Sequence↗

PubMed2000

In vivo study of tumor metabolism: an application of new multi-probe microdialysis system in the striatum of freely moving rats grafted with C6 cells.

The purpose of this study is to investigate the in vivo tumoral brain metabolism in free moving rats using microdialysis. Cells from C6 glioma cell line were inoculated in one striatum 15 days before the microdialysis experimentation. Then, using a new system allowing perfusion of several microdialysis probes in free moving rat, normalised dialysate levels of glucose, lactate and pyruvate were monitored in both glioma and control striatum. At the end of the procedure, animals were sacrificed for histological study. Data shows that probe functioning is similar in both tissues. The results for normalised glucose level were in striatum control: 2.14 mM, in tumoral striatum: 1.71 mM (P>0.1); for lactate, respectively, 0.86 and 1.65 mM (P<0.05) and for pyruvate, respectively, 65.56 and 140. 94 microM (P<0.05). This data clearly shows a significant increase of pyruvate and lactate in tumoral striatum compared to normal striatum, correlating previous in vitro studies on glioma metabolism. We conclude that this microdialysis technique is of value in tumoral brain and could constitute an interesting tool for a better understanding of glioma metabolism.

Animals↗

PubMed2000

Antimalarial, antitrypanosomal, and antileishmanial activities and cytotoxicity of bis(9-amino-6-chloro-2-methoxyacridines): influence of the linker.

Forty bis(9-amino-6-chloro-2-methoxyacridines), in which acridine moieties are joined by alkanediamines, polyamines, or polyamines substituted by a side chain, were synthesized and tested for their in vitro activity upon the erythrocytic stage of Plasmodium falciparum, trypomastigote stage of Trypanosoma brucei, and amastigote stage of Trypanosoma cruzi and Leishmania infantum as well as for their cytotoxic effects upon MRC-5 cells. Results clearly showed the importance of the nature of the linker and of its side chain for antiparasitic activity, cytotoxicity, and cellular localization. Among several compounds devoid of cytotoxic effects at 25 microM upon MRC-5 cells, one displayed IC(50) values ranging from 8 to 18 nM against different P. falciparum strains while three others totally inhibited T. brucei at 1.56 microM.

Acridines↗

PubMed2000

Synthesis and activity of pyrrolidinyl- and thiazolidinyl-dipeptide derivatives as inhibitors of the Tc80 prolyl oligopeptidase from Trypanosoma cruzi.

Pyrrolidinyl- and thiazolidinyl- dipeptide derivatives, featuring either a vinyl sulfone-, a 2-ketobenzothiazole-, a nitrile-, or a benzimidazole group at the C-terminus, were designed and synthesized as potential inhibitors of the prolyl-specific Tc80 proteinase from Trypanosoma cruzi, the agent of Chagas' disease. These compounds were evaluated in vitro towards the target enzyme which was classified as a serine protease belonging to the prolyl oligopeptidase family (EC 3.4.21.26). A peptidyl nitrile and two peptidyl alpha-ketobenzothiazoles were shown to be potent reversible and competitive inhibitors of Tc 80 proteinase, with K(i) values in the range 38-219 nM, and compared advantageously with some known mammalian prolyl oligopeptidase inhibitors.

Animals↗

PubMed2000

Intracellular targets of cyclin-dependent kinase inhibitors: identification by affinity chromatography using immobilised inhibitors.

BACKGROUND: Chemical inhibitors of cyclin-dependent kinases (CDKs) have great therapeutic potential against various proliferative and neurodegenerative disorders. Olomoucine, a 2,6,9-trisubstituted purine, has been optimized for activity against CDK1/cyclin B by combinatorial and medicinal chemistry efforts to yield the purvalanol inhibitors. Although many studies support the action of purvalanols against CDKs, the actual intracellular targets of 2,6, 9-trisubstituted purines remain unverified. RESULTS: To address this issue, purvalanol B (95. ) and an N6-methylated, CDK-inactive derivative (95M. ) were immobilized on an agarose matrix. Extracts from a diverse collection of cell types and organisms were screened for proteins binding purvalanol B. In addition to validating CDKs as intracellular targets, a variety of unexpected protein kinases were recovered from the 95. matrix. Casein kinase 1 (CK1) was identified as a principal 95. matrix binding protein in Plasmodium falciparum, Leishmania mexicana, Toxoplasma gondii and Trypanosoma cruzi. Purvalanol compounds also inhibit the proliferation of these parasites, suggesting that CK1 is a valuable target for further screening with 2,6,9-trisubstituted purine libraries. CONCLUSIONS: That a simple batchwise affinity chromatography approach using two purine derivatives facilitated isolation of a small set of highly purified kinases suggests that this could be a general method for identifying intracellular targets relevant to a particular class of ligands. This method allows a close correlation to be established between the pattern of proteins bound to a small family of related compounds and the pattern of cellular responses to these compounds.

Amino Acid Sequence↗

PubMed1999

Plasmepsin II, an acidic hemoglobinase from the Plasmodium falciparum food vacuole, is active at neutral pH on the host erythrocyte membrane skeleton.

Plasmepsin II, an aspartic protease from the human intraerythrocytic parasite Plasmodium falciparum, is involved in degradation of the host cell hemoglobin within the acidic food vacuole of the parasite. Previous characterization of enzymatic activities from Plasmodium soluble extracts, responsible for in vitro hydrolysis of erythrocyte spectrin, had shown that the hydrolysis process occurred at pH 5.0 and involved aspartic protease(s) cleaving mainly within the SH3 motif of the spectrin alpha-subunit. Therefore, we used a recombinant construct of the erythroid SH3 motif as substrate to investigate the involvement of plasmepsins in spectrin hydrolysis. Using specific anti-plasmepsin II antibodies in Western blotting experiments, plasmepsin II was detected in chromatographic fractions enriched in the parasite SH3 hydrolase activity. Involvement of plasmepsin II in hydrolysis was demonstrated by mass spectrometry identification of cleavage sites in the SH3 motif, upon hydrolysis by Plasmodium extract enzymatic activity, and by recombinant plasmepsin II. Furthermore, recombinant plasmepsin II digested native spectrin at pH 6.8, either purified or situated in erythrocyte ghosts. Additional degradation of actin and protein 4.1 from ghosts was observed. Specific antibodies were used in confocal imaging of schizont-infected erythrocytes to localize plasmepsin II in mature stages of the parasite development cycle; antibodies clearly labeled the periphery of the parasites. Taken together, these results strongly suggest that, in addition to hemoglobin degradation, plasmepsin II might be involved in cytoskeleton cleavage of infected erythrocytes.

Amino Acid Sequence↗

PubMed1999

Automated parallel synthesis of a tetrahydroisoquinolin-based library: potential prolyl endopeptidase inhibitors.

Solution-phase automated parallel synthesis of a Tic-based library is described. This library comprising 2560 members, was obtained from the combination of 80 carboxylic acids and 32 amines and was screened against Tc80 protease, a parasitic prolyl endopeptidase secreted by Trypanosoma cruzi. Pyrrolidine derivatives proved the most potent inhibitors with IC50 values found in the low nanomolar range.

Isoquinolines↗

PubMed1999

Involvement of calyculin A-sensitive phosphatase(s) in the differentiation of Trypanosoma cruzi trypomastigotes to amastigotes.

Differentiation of the non-dividing trypomastigote form of Trypanosoma cruzi, the causative agent of Chagas disease, to the dividing amastigote form normally occurs in cytoplasm of infected cells. Here we show that calyculin A. a potent inhibitor of protein phosphatases 1 and 2A, induces at pH 7.5 extracellular transformation of long slender trypomastigotes to round amastigote-like forms which acquire characteristic features observed after the normal differentiation process: repositioning and structural changes of the kinetoplast, release of surface neuraminidase, and expression of amastigote-specific epitopes. Calyculin A inhibits parasite phosphatases and changes in the phosphorylation of specific proteins occur during the transformation process. As an exposure of trypomastigotes to calyculin A concentrations as low as 1 nM and for only 1-2 h is sufficient to induce transformation, the inhibition of calyculin A-sensitive phosphatase(s) appears to play a major role in initiating the trypomastigote differentiation.

Animals↗

PubMed1999

Selective and reversible effects of vinca alkaloids on Trypanosoma cruzi epimastigote forms: blockage of cytokinesis without inhibition of the organelle duplication.

Vinca alkaloids, vincristine and vinblastine, produce differential effects on the cell division of Trypanosoma cruzi epimastigote forms depending on drug concentrations. These effects are related to different microtubule-based mechanisms. For 15 microM vinblastine and 50 microM vincristine, the drugs inhibit both nuclear division and cytokinesis, and affect cell shape. At 3 microM vinblastine and 10 microM vincristine, however, cytokinesis is inhibited without major effect on the progression of the cell cycle; this yields giant cells having multiple nuclei, kinetoplasts and flagella. Cultures maintained over 1 week with daily drug replacement produced cells with more than 16 nuclei and 24 kinetoplasts, indicating that an equivalent of a fifth cell cycle was initiated. The ultrastructure of the multinucleate cells showed a basic organization closely similar to that of trypanosomes. Cytokinesis inhibition by vinca alkaloids seems to result from modulations of interactions between microtubules and associated proteins, rather than from an inhibition of microtubule dynamics as is usually proposed for vinca alkaloids. Cytokinesis inhibition is reversible: after removing the drug, epimastigotes emerge from the multinucleate cells. The emerging process follows a precise axis and polarity which are determined by the position of the flagellum/kinetoplast complex. This region could play an essential role in cell morphogenesis since zoids (cells without a nucleus) are frequently observed.

Animals↗

PubMed1999

[Brain metastases and chemotherapy].

INTRODUCTION: The epidemiology of brain or central nervous system metastases is poorly documented. Retrospective studies based on autopsies that were aimed at investigating the incidence and prevalence of brain metastases have revealed the shortfalls in tumour registers. The exact role of cerebral metastases has not been addressed within the scope of cancer considered as a public health issue. CURRENT KNOWLEDGE AND KEY POINTS: The prognosis of brain metastases should not be considered either on general or a priori basis as being poorer than that of other metastatic sites. Evaluation of the role of focal radiation therapy and chemotherapy is still in progress. Appropriate use of therapeutical strategies directed at brain tumors generally improves the condition of most patients. It also usually increases survival and enhances the quality of life. FUTURE PROSPECTS AND PROJECTS: The role of chemotherapy in current therapeutical strategies has not yet been defined and should be investigated and developed.

Antineoplastic Agents↗

PubMed1999

Boron neutron capture enhancement (BNCE) of fast neutron irradiation for glioblastoma: increase of thermal neutron flux with heavy material collimation, a theoretical evaluation.

Despite the fact that fast neutron irradiation of glioblastoma has shown on autopsies an ability to sterilize tumors, no therapeutic windows have been found for these particles due to their toxicity toward normal brain. Therefore, the Boron Neutron Capture Enhancement (BNCE) of fast neutron beam has been suggested. This paper addresses the problem of fast neutron beam collimation, which induces a dramatic decrease of the thermal neutron flux in the depth of the tissues when smaller irradiation fields are used. Thermoluminescent dosimeter TLD-600 and TLD-700 were used to determine the thermal neutron flux within a Plexiglas phantom irradiated under the Nice Biomedical Cyclotron p(60)+Be(32) fast neutron beam. A BNCE of 4.6% in physical dose was determined for a 10 x 10 cm2 field, and of 10.4% for a 20 x 20 cm2 one. A Dose Modification Factor of 1.19 was calculated for CAL 58 glioblastoma cells irradiated thanks to the larger field. In order to increase the thermal flux in depth while shaping the beam, heavy material collimation was studied with Monte Carlo simulations using coupled FLUKA and MCNP-4A codes. The use of 20 cm width lead blocks allowed a 2 fold thermal neutron flux increase in the depth of the phantom, while shielding the fast neutron beam with a fast neutron dose transmission of 23%. Using the DMF of 1.19, a BNCE of 40% was calculated in the beam axis. This enhancement might be sufficient to open, at least theoretically, a therapeutic window.

Beryllium↗

PubMed1999

Occipitocervical fixation using hooks and screws for upper cervical instability.

OBJECTIVES: Occipitocervical fixation is used for the treatment of nontraumatic upper cervical instabilities. To date, plates have been fixed with screws or wires. However, these devices are not indicated in the treatment of patients with severe osteoporosis or in instances of significant thinning of the occipital bone. We performed a clinical trial of a new type of fixation that uses cervical interlaminar hooks and occipital claws with hooks or with screws (CCD type; Sofamor-Danek, Roissy, France) for the treatment of nontraumatic upper cervical instabilities. METHODS: Five women and one man ranging in age from 28 to 72 years (average age, 54 yr) were thus treated. The CCD type material had two rod plates and hooks allowing the proper placement of interlaminar and occipital claws. The occipital plate can also be directly screwed to the bone. Occipital hooks were used in four patients. The other two patients, who had occipitocervical congenital abnormalities that required an occipitocervical opening and an additional dural enlargement, underwent occipital screw fixation because of the previous opening of the foramen magnum. A cancellous iliac autograft allowed the usual fusion. RESULTS: No postoperative complications were observed, and all patients experienced significant improvement of their neck pain. Four patients had neurological symptoms. The condition of two patients improved, and the condition of the other two stabilized. CONCLUSION: This report confirms the interest of the CCD method to correct all types of upper cervical instabilities, even in cases of unusual thinning of the occipital bone or in osteoporotic states.

Adult↗

PubMed1999

Identification of inhibitors of an 80 kDa protease from Trypanosoma cruzi through the screening of a combinatorial peptide library.

Two orthogonal peptide combinatorial libraries were screened to discover inhibitors of Tc80 protease, a novel target from Trypanosoma cruzi involved in host cell invasion. These libraries were composed of 15,625 structurally diversified tripeptides, partitioned in 125 mixtures. The screening led to a low micromolar inhibitor which was actually an HF cleavage by-product H-Ipe-D-Tic-D-Glu(S-paratolyl)-OH. IC50 values of several analogous molecules of this hit were determined and are discussed. For the best compounds, conformational analysis revealed a high degree of similarity in shape with a potent prolylendopeptidase inhibitor, SUAM-1221.

Animals↗

PubMed1998

Expression of insulin-like growth factor-binding protein 6 complementary DNA alters neuroblastoma cell growth.

Insulin-like growth factors I and II (IGF-I and IGF-II) are actively involved in neuroblastoma cell growth. In all biological fluids, they are noncovalently bound to high-affinity binding proteins. At least six species of these IGF-binding proteins (IGFBPs) have been identified, but their precise roles remain unclear. One of them, IGFBP-6, is produced by neuroblastoma cells in culture under certain experimental conditions and seems to be associated with the arrest of cell growth. We stably transfected IGR-N-91 and SK-N-SH neuroblastoma cells with an expression vector comprising IGFBP-6 cDNA, whose expression was placed under the control of the constitutive and ubiquitous cytomegalovirus promoter. Analyses of the cell cycle (flux cytofluorometry), mitogenic activity (radiolabeled thymidine incorporation), and the number of viable cells (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test) showed that the mitogenic effects of serum, IGF-I, IGF-II, and des (1-3) IGF-I, a truncated IGF-I analogue with no affinity for IGFBP-6, were depressed in both transfected cell lines. With s.c. injection of transfected IGR-N-91 cells into nude mice, tumors developed in only 50-70% of cases, 1 or 2 weeks after those in controls, and were 60-90% smaller. Our findings show that IGFBP-6 influences neuroblastoma cell growth, both in vitro and in experimental xenograft development.

Animals↗

PubMed1998

Endodermal cyst of the foramen magnum: case report and review of the literature.

The majority of endodermal cysts occur in the cervicothoracic spine, ventral to the cord. Intracranial locations are rare. We report a case involving the foramen magnum in a 14-year-old child, which was an incidental finding following a traumatic head injury. A review of the literature revealed six other cases involving this same location. These lesions are asymptomatic for a long time, and may cause brain stem medullary compression. Treatment is surgical. Effective simple removal can be achieved by a posterior approach.

Adolescent↗

PubMed1998

Chiari Type I malformation and syringomyelia in unrelated patients with blepharophimosis. Report of two cases.

Syringomyelia is a rare, mainly sporadic disease of the spinal cord, which is associated with 80% of cases in which a Chiari Type I malformation is also present. A mendelian transmission of syringomyelia (autosomal dominant or recessive) has been proposed in approximately 2% of reported cases. The association of syringomyelia with hereditary diseases (Noonan's syndrome, phacomatoses) has been mentioned frequently in the literature. The authors report the presence of a Chiari Type I malformation accompanied by syringomyelia in two unrelated patients affected by a familial Type II blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). The first patient was a 35-year-old woman who presented with a right C-8 root paresia. The second case involved a 20-year-old man who complained of cervical radicular pain. Both belong to families in which BPES was segregated in an autosomal dominant modality, but other family members had no known neurological symptoms. To the authors' knowledge, such a combination has never been described. Perhaps the possible involvement of a genetic component in some cases of Chiari Type I-associated syringomyelia will someday be debated.

Adult↗

PubMed1998

Photodecontamination of blood components: advantages and drawbacks.

Photochemical methods using photosensitizing photoactive drugs are very promising for blood product decontamination. Depending on the nature of virus - or parasite - bound photosensitizers, direct photochemical addition to virus components (DNA, proteins and lipids) occurs or the photosensitizer produces singlet oxygen inactivating viruses or parasites. The main advantage of this method is the lack of dark toxicity of presently used photosensitizers (psoralens, methylene blue, merocyanine 540, porphyrins/chlorins, phthalocyanines). In blood, the uptake of photosensitizers is not fully specific for infected cells. Therefore, normal cells and plasma proteins may suffer from the photodynamic action. Consequently, cell metabolism, rheological properties and surface markers may be altered and a slow loss of functionality occurs during storage. Data regarding pathogen inactivation in plasma and blood proteins, platelets and RBC concentrates are presented in comparison with the effect of photosensitization on normal blood components. Means for protecting normal components from photosensitization are also evaluated.

Blood Transfusion↗

PubMed1998

[Extracranial trigeminal schwannomas with middle temporal fossa development].

Schwannomas of trigeminal nerve account for 0.07% to 0.36% of all intra-cranial tumors. We report three observations about Jefferson's type D tumors, mainly extra-cranial with only small intra-cranial extension, concerning two men and one woman, who were respectively 36, 60 and 63 years old. Two of them presented with facial pain and hypoesthesia in the same territory. The third one developed a diplopia. In all cases, CT scanner analysis evidenced a large hypodense tumor extending in the infratemporal fossa. Temporal lobe and cavernous sinus were pushed aside by the intra-cranial extension. Tumors were hypo intense in T1-weighted image with significant enhancement after gadolinium injection. One of the tumors was a cystic form and in that case, an hyper signal in T2-weighted image was detected in the middle of the lesion. A combined subtemporal and transmaxillary approach was performed in 2 cases. In the third case, the removal of the tumor was only performed by a transmaxillary approach. In this series, there was no surgical mortality. One patient presented a postoperative residual painful anesthesia. In conclusion, extra-cranial schwannomas with intra-cranial extension are specially rare lesions. The most common early symptoms are facial neuralgia, facial hypoesthesia or diplopia. Neuroradiologic investigations, including CT and MRI evidence the precise anatomic site of the lesions. With the help of these techniques, total surgical tumor removal is possible in the majority of cases.

Adolescent↗