Biomedical subjects
Publications and source records attributed to R Faure.
The (1)H and (13)C NMR resonances for forty-three 2-aryl and 2-N-arylamino benzothiazole derivatives were completely assigned using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC).
Mutations in the EIF2AK3 gene have been identified in patients with Wolcott-Rallison syndrome - a rare autosomal recessive disorder associated with permanent neonatal insulin-dependent diabetes. Despite the fact that different mutations have been observed in every single unrelated case reported so far, most patients presented with similar characteristics, such as osteopenia, epiphyseal dysplasia as well as hepatic and/or renal dysfunction. The EIF2AK3 gene was analyzed using a PCR-based sequencing approach in two Wolcott-Rallison patients and their parents. We report two cases from different families carrying the same and novel truncating nonsense mutation in the EIF2AK3 gene that encodes the pancreatic eukaryotic initiation factor 2alpha kinase 3. This mutation clearly displays different clinical characteristics in the two patients we examined. Remarkably, the onset of diabetes was different for the two patients, and there was also heterogeneity in other clinical manifestations. These cases illustrate the important role of alternative pathways that could, to some extent, take over or supplement a defective metabolic pathway. This supports the idea that there is no simple relationship among clinical manifestations and EIF2AK3 mutations.
Three new friedelane-type triterpenoids, 3,4-secofriedelan-3,28-dioic acid (1), 27-hydroxyacetate canophyllic acid (2) and 3-oxo-27-hydroxyacetate friedelan-28-oic acid (3), were isolated from the leaves of Calophyllum inophyllum (Clusiaceae) grown in French Polynesia. Their structures were established by the concerted application of 2D NMR techniques including gs-COSY, gs-HMQC and gs-HMBC.
Detailed (1)H and (13)C NMR assignments of 3alpha-5alpha-tetrahydrodeoxycordifoline lactam and cadambine acid, isolated from the bark of the Nauclea diderrichii (de Wild.) Merr. (Rubiaceae) were achieved by 1D and 2D techniques such as DEPT, HMBC, HMQC, COSY and NOESY.
The 1H and 13C NMR resonances of 15 N,N'-diacylproflavines were assigned completely and unequivocally using a concerted application of one- and two-dimensional experiments (DEPT, gs-COSY, gs-HMQC and gs-HMBC).
Three new cadinane- and guaiane-type sesquiterpenoids, 2-hydroxy-10-epi-zonarene 1, 2, 15-dihydroxycalamenene 2 and guaia-4, 6-dien-3-one 3, were isolated from the wood of Enterospermum madagascariensis (Rubiaceae) grown in Madagascar. Their structures were established from concerted application of 2D NMR techniques including gs-COSY, gs-HMQC, gs-HMBC and NOESY.
The ability of bone charcoal to remove Cr(III) from aqueous solutions by adsorption has been investigated. The adsorbent used was first characterised and then the adsorption was studied as a function of time and amount of charcoal. Tests were carried out with synthetic solutions whose Cr concentrations (500 mg L(-1)) were similar to those found in some effluents of Moroccan tannery industries. Cr removal efficiencies higher than 90% were obtained at pH 3.5 using 3 g of bone charcoal and a stirring time of about 30 min. Results of Cr removal by all sieved fractions of bone charcoal had shown the same interesting capabilities for Cr(III) retention. The cross interference with other elements was also investigated. Pre-treatment of bone charcoal by nitric acid led to an increase in its specific surface area but induced a drastic reduction in its Cr elimination abilities. Adsorption tests were also carried out using calcinated bone charcoal. The results obtained showed a similar percentage of Cr retention to those found with untreated bone charcoal. On the other hand, a double treatment of bone charcoal with HCl and NaOH provided an enhancement of Cr(III) retention. The role played by the mineral fraction of the solid phase of bone was thus evidenced.
alpha,alpha'-Diactivated cyclic- or acyclic ketones undergo a chemoselective base promoted (K2CO3, DBU) one-pot C-C cycloalkylation, with 1,3- and 1,4-dihalides having a cis-like fixed configuration. This reaction gives highly functionalized bicyclo[3.2.1]octan-9-one and bicyclo[4.2.1]nonan-9-one derivatives, which are easily transformed to seven- and eight-membered rings through a high yield retro-Dieckmann cleavage. Starting from trans-1,4-dibromo-2-butenes, the transformation is governed by stereoelectronic factors and leads, through a chemo- and stereoselective C-O cycloalkylation, to synthetically valuable monocyclic or fused polycyclic functionalized enol ethers of high synthetic value. Semiempirical calculations showed a small difference in energy and the late character of the transition states leading to cis and trans isomers of the corresponding fused polycyclic enol ethers. These results, although minimizing the influence of a destabilizing 1,3-interaction on the outcome of the reaction, are qualitatively in agreement with the experimental results.
Fifteen triterpenoid saponins were isolated from the berries of Hedera colchica and their structures established on the basis of chemical and spectroscopic evidence. Among them, two are new compounds: coichiside A (3) and colchiside B (15) and four are described for the first time in the berries of Hedera colchica (compounds 1, 8, 9 and 11).
During interphase the transport of material between different intracellular organelles requires accurate regulation of fusiogenic domains. Recent studies on hepatic endosomes indicated that compartmentalized Cdk2-cyclin E complexes act by braking fusion events. These Cdk2 complexes integrate tyrosine phosphorylation and dephosphorylation inputs, resulting in the control of the number of rounds of fusion at discrete domains. This leads to changes in the intracellular location of internalized receptors and ultimately their biological response.
Little is known about cell-cycle checkpoint activation by oxidative stress in mammalian cells. The effects of hyperoxia on cell-cycle progression were investigated in asynchronous human T47D-H3 cells, which contain mutated p53 and fail to arrest at G1/S in response to DNA damage. Hyperoxic exposure (95% O(2), 40-64 h) induced an S-phase arrest associated with acute inhibition of Cdk2 activity and DNA synthesis. In contrast, exit from G2/M was not inhibited in these cells. After 40 h of hyperoxia, these effects were partially reversible during recovery under normoxic conditions. The inhibition of Cdk2 activity was not due to degradation of Cdk2, cyclin E or A, nor impairment of Cdk2 complex formation with cyclin A or E and p21(Cip1). The loss of Cdk2 activity occurred in the absence of induction and recruitment of cdk inhibitor p21(Cip1) or p27(Kip1) in cyclin A/Cdk2 or cyclin E/Cdk2 complexes. In contrast, Cdk2 inhibition was associated with increased Cdk2-Tyr15 phosphorylation, increased E2F-1 recruitment, and decreased PCNA contents in Cdk2 complexes. The latter results indicate a p21(Cip1)/p27(Kip1)-independent mechanism of S-phase checkpoint activation in the hyperoxic T47D cell model investigated.
The phosphotyrosine phosphatase inhibitor bpV(phen) has the ability to markedly decrease the progression of leishmaniasis in vivo. Here, we have identified the mechanisms that are responsible for this protective effect. We report that two potent peroxovanadium (pV) compounds, bpV(phen) and bpV(pic), control progression of leishmaniasis in a similar manner by modulating NO-dependent microbicidal action. We observed that their injection can rapidly and transiently induce the expression of inducible NO synthase (iNOS) in livers of mice and enhance circulating nitrate levels. Treatment of mice with bpV(phen) or bpV(pic) completely controlled progression of leishmaniasis in an NO-dependent manner, since inhibition of iNOS with aminoguanidine completely reversed this pV-mediated protection. This NO-dependent pV-mediated protection was further demonstrated by the incapacity of bpV(phen)-treated Nramp-/-, iNOS-/- mutant mice to control Leishmania major infection. Using an air pouch model, we showed that bpV(phen) can strongly modulate secretion of L. major-induced pro-inflammatory molecules and neutrophil recruitment. In addition, we observed that bpV(phen) per se can strongly induce the expression of Th1 type cytokines over Th2 in spleens of animals. Overall, this study has allowed us to establish the in vivo functional and immunological events involved in pV-mediated protective mechanism against leishmaniasis and that NO plays a pivotal role in this process.
The isolation of flavonol glycosides 1-3 from the leaves of Ipomoea fistulosa is reported.
Two new triterpenoid saponins, glinosides A and B, isolated from the aerial parts of Glinus oppositifolius, have been characterized by 1D, 2D, NMR and high-resolution mass spectral (HRMS) techniques. Their structures were established respectively as 16-O-(beta-arabinopyranosyl)-3-oxo-12,16 beta,21 beta,22-tetrahydroxyhopane for glinoside A and 16-O-(beta-arabinopyranosyl)-3-oxo-12,16 beta,22-trihydroxyhopane for glinoside B. Results presented evidence that fractions had a better antiplasmodial activity (IC50 = 31.80 micrograms/ml) than pure glinoside A (IC50 = 42.30 micrograms/ml).
It has been suggested that proteins of molecular size 56-58 kDa play an important role in bovine ovarian follicular development and oocyte maturation. A polyclonal antibody was raised against a 56- to 58-kDa protein band purified from bovine granulosa cells and was used to screen granulosa or luteal cell cDNA expression libraries. This work resulted in the identification of a cDNA encoding for a protein of 60.1 kDa with a signal peptide of 13 residues. The bovine 60.1-kDa protein shared an overall 86.7% and 81.8% identity with, respectively, the human 80K-H protein and the mouse putative beta subunit of glucosidase II (beta-GII), and was named vacuolar system-associated protein-60 (VASAP-60). Marked differences in sequence identity were noted in a putative molecular adapter domain containing a tandem D and E amino acid stretch flanked by proline-rich sequences presenting the minimal PXXP SH3 motif. VASAP-60 was shown to be unglycosylated using endoglycosidase H treatment and was found mainly in a cellular membrane fraction of bovine corpus luteum. VASAP-60 was localized in a rat hepatic Golgi/endosome fraction and in wheat germ agglutinin (WGA) affinity chromatographic eluates, thereby suggesting the presence of interactions with membrane glycoproteins. A polyclonal antibody was raised against the putative adapter domain of the recombinant VASAP-60; this was shown to recognize a major 88-kDa and two minor 58-kDa and 50-kDa proteins, suggesting that the major 88-kDa protein band represents the complete VASAP-60 protein whereas the 58-kDa and the 50-kDa bands represent its proteolytic fragments. Northern blot analysis demonstrated the presence of a single 2.3-kilobase transcript in all the bovine tissues analyzed with variation in the steady state level between tissues. Immunohistochemical observations showed that VASAP-60 was widely distributed in bovine tissues and was localized in pericytoplasmic and perinuclear membranes. In epithelial cells, the staining presented a basolateral or apical polarity associated with intracellular vacuoles. In conclusion, we have characterized a novel acidic membrane protein, associated with organelles of the vacuolar system, that is widely and histospecifically expressed in bovine tissues. VASAP-60 represents either the bovine ortholog or a new family member of the previously characterized human 80K-H and murine beta-GII proteins. Our results suggest that VASAP-60 presents characteristics of a molecular adaptor protein with functions in membrane-trafficking events.
Exposure of target cells to insulin results in the formation of ligand receptor complexes on the cell surface and their subsequent internalization into the endosomal apparatus. A current view is that endocytosis of the insulin receptor (IR) kinase results in its rapid deactivation and sorting of the IR back to the cell surface or to late endocytic compartments. We report herein that, in skeletal muscle, in vivo stimulation with insulin induced a rapid internalization of the IR to an insulin-sensitive GLUT4-enriched intracellular membrane fraction. After 30 min of stimulation, IR content and tyrosine phosphorylation were increased by three and nine times in that fraction, respectively, compared with unstimulated muscles. In vitro autophosphorylation assays revealed that the kinase activity of internalized IRs was markedly augmented (eight to nine times) by insulin. In marked contrast with hepatic endosomes or adipocyte low-density microsomes, no IR tyrosine dephosphorylation activity was observed in GLUT4-enriched vesicles isolated from skeletal muscle. The activated IR was recovered in immunopurified GLUT4 vesicles after insulin stimulation. Insulin also increased tyrosine-phosphorylated insulin receptor substrate 1 and phosphatidylinositol 3-kinase adapter (p85) subunit contents in the intracellular membrane fraction, but these signaling molecules were not directly associated with GLUT4 vesicles. These results show that, in skeletal muscle, the activated IR reaches a GLUT4-enriched compartment where its activity is apparently sustained. We propose that compartmentalization of activated IRs to GLUT4 vesicles may play a role in sustaining insulin signaling at this locus in skeletal muscle.
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Leishmania-induced macrophage (Mphi) dysfunctions have been correlated with altered signaling events. Recent findings from our laboratory suggest that modulation of host protein tyrosine phosphatase (PTP) following Leishmania infection could lead to these Mphi defects. To address this issue, Mphi PTP activity and IFN-gamma-inducible signaling events were evaluated in Leishmania donovani (Ld)-infected cells. We observed that Ld promastigotes can rapidly trigger host PTP activity simultaneously with dephosphorylation of Mphi protein tyrosyl residues and inhibition of protein tyrosine kinase (PTK). Our results further revealed that Mphi SHP-1 PTP was rapidly activated by the infection. This Ld-evoked signaling alteration was reflected by absence of IFN-gamma-induced intracellular phosphorylation. IFN-gamma-inducible JAK2 PTK phosphorylation was also markedly diminished in Ld-infected cells. We also observed that co-immunoprecipitation of JAK2 with SHP-1 was considerably higher in infected as compared to uninfected cells. Altogether, these results suggest that SHP-1-mediated JAK2 dephosphorylation triggered by Leishmania is partly responsible for abnormal Mphi IFN-gamma signaling and represent an important mechanism supporting persistent parasitic infection.