Electrochemical investigation of the P2­NaxCoO2 phase diagram.

Sodium layered oxides NaxCoO2 form one of the most fascinating low-dimensional and strongly correlated systems; in particular P2­NaxCoO2 exhibits various single-phase domains with different Na+/vacancy patterns depending on the sodium concentration. Here we used sodium batteries to clearly depict the P2­NaxCoO2 phase diagram for x≥0.50. By coupling the electrochemical process with an in situ X-ray diffraction experiment, we identified the succession of single-phase or two-phase domains appearing on sodium intercalation with a rather good accuracy compared with previous studies. We reported new single-phase domains and we underlined the thermal instability of some ordered phases from an electrochemical study at various temperatures. As each phase is characterized by the position of its Fermi level versus the Na+/Na couple, we showed that the synthesis of each material, even in large amounts, can be carried out electrochemically. The physical properties of the as-prepared Na1/2CoO2 and Na2/3CoO2 ordered phases were characterized and compared. Electrochemical processes are confirmed to be an accurate route to precisely investigate in a continuous way such a complex system and provide a new way to synthesize materials with a very narrow existence range.

NMR study of the LiMnPO(4)·OH and MPO(4)·H(2)O (M = Mn, V) homeotypic phases and DFT calculations.

Following our previous work on the tavorite-like LiFePO(4)·OH and FePO(4)·H(2)O phases, we report here the magnetic and NMR characterizations of analogous LiMnPO(4)·OH, MnPO(4)·H(2)O and VPO(4)·H(2)O phases together with the DFT calculations of the NMR shifts. The first two compounds exhibit Curie-Weiss type magnetic behavior with Curie constants close to the theoretical ones for HS Mn(3+), while the vanadium compound is very close to a pure Curie-type behavior. (7)Li, (31)P and (1)H MAS NMR spectra are reported for the three compounds, and show strong Fermi-contact shifts for the first two nuclei, while the sign and magnitude of the (1)H shifts are very different for the three phases. DFT calculations (FLAPW in GGA+U approximation) using the WIEN2k code and the experimental susceptibilities are shown to reproduce closely the experimental data. This situation is compared to the case of the homologous and isostructural Fe compounds, which exhibit much more complex magnetic behaviors.

Reinvestigation of the OP4-(Li/Na)CoO2-layered system and first evidence of the (Li/Na/Na)CoO2 phase with OPP9 oxygen stacking.

The composition and synthesis conditions of the (Li/Na)CoO(2) phase with an ordered 1:1 Li/Na stacking alternating with CoO(2) slabs were determined from a careful study of the P2-Na(∼0.7)CoO(2)-O3-LiCoO(2) system. An in situ X-ray diffraction (XRD) thermal study emphasizes the metastable character of this phase that can be stabilized only by very fast quenching. Its composition, (Li(0.42)Na(0.37))CoO(2), is significantly different from the ideally expected one, (Li(0.50)Na(0.35))CoO(2), and its structure, confirmed by Rietveld refinement of the XRD pattern, presents an ideal alternate ordering of lithium, cobalt, and sodium layers within OP4-type oxygen packing. The presence of vacancies in both alkali-ion layers was confirmed by electrochemical intercalation of lithium and sodium. For the first time, a new type of layered oxide exhibiting OPP9-type oxygen packing was evidenced. Between the CoO(2) slabs, alkali ions are intercalated in the following order: Li(octa)-Na(prism)-Na(prism). This material crystallizes in the R3m space group with a(hex) = 2.828 Šand c(hex) = 46.85 Šcell parameters.

Cytarabine and cisplatin as salvage therapy in patients with metastatic colorectal cancer who failed 5-fluorouracil + folinic acid regimen. French Northern Oncology Group.

The combination of CDDP and ARA-C has shown some clinical efficiency as first-line therapy in advanced colorectal cancer. Our study was aimed to evaluate the therapeutic activity of this combination in advanced colorectal cancer who failed 5-fluorouracil (FU) and folinic acid (LV) regimen. Seventeen patients with measureable metastatic colorectal cancer who failed 5FU-LV therapy as first line (n = 14) or second line treatment (n = 3), entered the study. Three patients who recurred during adjuvant treatment with 5FU and levamisol, were also included. Median age was 59.5 (40-69). Performance status was as follows: 0 (n = 5), 1 (n = 11), 2 (n = 3), 3 (n = 1). Site of metastases included liver (n = 16), lung (n = 7), abdomen (n = 2), pelvic recurrences (n = 2), cutaneous (n = 1). Seven patients had 2 metastatic sites and two 3. The treatment was given as follows: ARA-C 75 mg/m2/day, days 1-3, followed 1 hour later by CDDP 30 mg/m2/day, days 1-3, every 28 days. The median number of cycles was 3 (range: 1-6 cycles). All patients but one were evaluable for both response and toxicity. Of these patients, 50% experienced severe hematologic toxicity and nonhematologic toxicity mainly consisted of fatigue and/or vomiting. No objective response was observed, but there were 3 stabilizations and 16 progressive diseases. Median time to progression was 10 weeks. Thus, the CDDP/ARA-C regimen is not of clinical value as salvage therapy in advanced colorectal cancer because of its toxicity and its lack of efficiency.

Epidemic cluster of legionnaires disease in Paris, June 1998.

From 29 June to July 1998, four cases of legionnaires disease in British citizens were reported to the Reseau National de Sante Publique (RNSP) by the statutory notification system (declaration obligatoire (DO)) and by theEuropean Surveillance Scheme for

[Granisetron (per os) compared with ondansetron (per os) in the prevention of nausea and vomiting induced by mildly emetogenic chemotherapies. Groupe de Recherches en Cancerologie du Nord]. / Granisétron (per os) comparé à ondansétron (per os) dans la prévention des nausées et vomissements induits par des chimiothérapies moyennement émétisantes. Groupe de recherche en cancérologie du Nord.

It is a randomised cross-over multicenter study comparing the efficacy and the tolerance of granisetron (Gra) 1 mg and ondansetron (Ond) 8 mg, oral, given during two consecutive cycles to 188 naive patients scheduled to receive a moderately emetogenic chemotherapy. The antiemetic treatment is given one day per course, 1 hour before chemotherapy and the second administration from 8 to 12 hours after the beginning, during each of the two cycles; alternatively according to the randomisation. Five criteria are assessed; nausea (ordinal and visual analogic scales), emeric episodes (vomiting orland retching), complete response (minor or no nausea, no emetic episode and no rescue treatment), patient preference and tolerance. The intent to treat analysis showed no significant difference at cycle 1 between Gra and Ond; at cycle 2, there is no significant difference in the number of emetic episodes; for the prevention of nausea, the ordinal scale shows a significant difference (p = 0.028 in favour of Gra at day 1 (D1) but not from D2 to D5. Gra induced more complete response than Ond at D1 (p = 0.028), but not from D2 to D5. The cross-over study did not show any period or order effect, whereas a treatment effect on Ond was significant in favour of Gra (p = 0.01). There is no significant patients preference in favour of Gra or Ond. In conclusion, Gra was more efficient in preventing nausea and obtaining complete response on the first day of treatment, significantly at the second cycle. Both Gra and Ond had a good antiemetic activity for moderately emetogenic chemotherapy with complete response rates always over 50% on day 1; delayed emesis remain less weli controlled.

The P2-Na(2/3)Co(2/3)Mn(1/3)O2 phase: structure, physical properties and electrochemical behavior as positive electrode in sodium battery.

Manganese substituted sodium cobaltate, Na(2/3)Co(2/3)Mn(1/3)O(2), with a layered hexagonal structure (P2-type) was obtained by a co-precipitation method followed by a heat treatment at 950 °C. Powder X-ray diffraction analysis revealed that the phase is pure in the absence of long-range ordering of Co and Mn ions in the slab or Na(+) and vacancy in the interslab space. The oxidation states of the transition metal ions were studied by magnetic susceptibility measurements, electron paramagnetic resonance (ESR) and (23)Na magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The charge compensation is achieved by the stabilization of low-spin Co(3+) and Mn(4+) ions. The capability of Na(2/3)Co(2/3)Mn(1/3)O(2) to intercalate and deintercalate Na(+) reversibly was tested in electrochemical sodium cells. It appears that the P2 structure is maintained during cycling, the cell parameter evolution versus the sodium amount is given. From the features of the cycling curve the formation of an ordered phase for the Na(0.5)Co(2/3)Mn(1/3)O(2) composition is expected.

The C terminus of the hepatitis B virus e antigen precursor is required for a tunicamycin-sensitive step that promotes efficient secretion of the antigen.

The Hepatitis B virus encodes the secreted e antigen (HBe) whose function in the viral life cycle is unknown. HBe derives from a 25-kDa precursor that is directed to the secretory pathway. After cleavage of the signal sequence, the resulting 22-kDa protein (P22) is processed in a post-endoplasmic reticulum compartment to mature HBe by removal of the 34-amino acid C-terminal domain. The efficiency of HBe secretion is specifically decreased in cells grown in the presence of tunicamycin, an inhibitor of N-glycosylation. Inasmuch as HBe precursor is not N-glycosylated, our data suggest that a cellular tunicamycin-sensitive protein increases the intracellular transport through the HBe secretory pathway. The study of the secretion of HBe derived from C-terminal-truncated precursors demonstrates that the tunicamycin-sensitive secretion absolutely requires a part of the C-terminal region that is removed to form mature HBe, indicating that the cellular tunicamycin-sensitive protein increases the efficiency of the intracellular transport of P22. We have also shown that the Escherichia coli beta-galactosidase can be secreted when fused to the HBe precursor signal sequence and that the P22 C-terminal domain renders the secretion of this reporter protein also tunicamycin-sensitive.

Characterization and biosynthesis of the woodchuck hepatitis virus e antigen.

The biosynthesis of the secretory core gene product of the woodchuck hepatitis virus (WHV) was studied in human cells. We have shown that the WHV e antigen was a N-glycosylated (most likely a diglycosylated) protein, with an apparent M(r) of 24K. To demonstrate that the WHV precore protein was correctly processed in human cells, we engineered chimeric proteins in which signal peptides or arginine-rich domains of WHV and hepatitis B virus (HBV) precore proteins were exchanged. Our results showed that both the signal peptide and the arginine-rich region of WHV precore protein were cleaved off during the secretion pathway, as previously reported for precore protein of human HBV and duck HBV. These observations demonstrate that the maturation process of the e antigen is conserved in hepadnaviruses. In addition, on the basis of inhibition experiments, we suggest that the cleavage of the carboxy terminus of the WHV precore protein occurred in a post-endoplasmic reticulum compartment, most likely beyond the medial Golgi, and that this cleavage was catalysed by an aspartyl protease.

[Effect of an electric field on the penetration of fluorides into dental enamel, studied in vitro and in vivo]. / Influence d'un champ électrique sur la pénétration du fluor dans l'émail dentaire étudiée "in vitro" et "in vivo"

The aim of the present study is to determine the influence of iontophoresis on the deposition of fluorine in dental enamel. A micromethod of fluorine-deposition and of dental enamel-sampling was perfected in vitro; it was then applied in vivo. Fluorine was layed down by topical and iontophoretical way, under the form of sodium fluoride in neutral solution. In in-vitro and in 2 in-vivo asseys 18F was used as an indicator, while in other ones fluorine was titrated by mean of a specific lanthan-fluoride electrode. Results from both methods agree. It is stated that the fluorine deposition on enamel remains lightly but significantly higher, in vivo as well as in vitro, when the tooth is subjected to a continuous electrical field.

Structural study of the T#2-LixCoO2 (0.52 < x < or = 0.72) phase.

The metastable O2-LiCoO(2) phase undergoes several reversible phase transitions upon lithium deintercalation. The first transition leads to an unusual oxygen stacking in such layered compounds. This stacking is found to be stable for 0.52 < x < or = 0.72 in Li(x)()CoO(2) and is called T(#)2. We studied this phase from a structural viewpoint using X-ray and neutron diffraction (ab initio method). The new stacking derives from the O2 one by gliding every second CoO(2) slab by (1/3, 1/6, 0). The lithium ions are found to occupy very distorted tetrahedral sites in this structure. We also discuss the possibility of this T(#)2 phase to exhibit stacking faults, whose amount depends on the method used to prepare this deintercalated phase.

Identification of a cellular protein specifically interacting with the precursor of the hepatitis B e antigen.

In hepatitis B virus (HBV) the precore gene encodes a protein from which derives P22, the precursor of the mature secreted hepatitis B virus e antigen (HBeAg). Circumstantial evidences suggest that HBeAg and/or its precursor P22 are important for establishing persistent infection. Although P22 is essentially present in the secretory pathway, a substantial fraction has been found in the cytosol. In order to get new insights into the biological function of P22, we looked for cellular proteins which could strongly associate with this protein. Using immunoprecipitation studies on human cell extracts, we found that a non-secreted cellular protein of about 32 kDa (P32) bound with a high specificity to P22. P32 associated neither with HBeAg nor with the viral core protein P21 which exhibits the same amino acids sequence as P22 but is N-terminally shorter by 10 residues. We also demonstrated that this interaction depended on the presence of the P22 C-terminal domain. Our data argues for a potential biological function of P22.

Importance of the C terminus of the hepatitis B virus precore protein in secretion of HBe antigen.

The hepatitis B virus (HBV) e antigen (HBeAg) is a 15 kDa soluble antigen derived from a precursor protein (precore protein) by two processing events, cleavage of the N-terminal signal peptide and cleavage of the C-terminal 34 amino acids. So far, the role of the C-terminal sequences in secretion has not been analysed in full. In this study deletion of the last 60 amino acids was found to abrogate HBeAg secretion whereas deletions of the last 10, 25 or 39 amino acids decreased its secretion rate. These data demonstrate that C-terminal precore protein sequences are crucial for HBe secretion and determine its secretion rate.

Biosynthesis of hepatitis B virus e antigen: directed mutagenesis of the putative aspartyl protease site.

The C gene products of all mammalian hepadnaviruses contain a region with sequence similarities to the catalytic center of the aspartyl proteases. This region could have the capacity to cleave precore proteins, leading to the synthesis of e antigen. By site-directed mutagenesis on a plasmid containing the hepatitis B virus C gene, we have replaced either the Asp residue of the putative aspartyl protease catalytic center or an Asp residue located 3 amino acids upstream. Transient expression of the mutated hepatitis B virus C gene in human and mouse cells showed that none of these mutations prevented the secretion of an accurately processed HBe antigen. Thus, we demonstrated that the aspartyl protease responsible for e antigen precursor processing is not C gene encoded but is more likely to be a cellular enzyme. From these results, we suggest a model for the mechanism of e antigen synthesis.

[Methods of determination of fluoride in trace amounts. Application to the study of the diffusion of fluoride from an amalgam in dental tissues]. / Les méthodes de dosage du fluor à l'état de trace. Application à l'étude de la diffusion du fluor apporté par un amalgame dans les tissus dentaries

The study of fluoride diffusion in dental tissues has been performed by microprobe analysis. The fluoride supply is carried out in vivo by various fluorides added to conventional amalgams. This method differs then from previous work (topical applications, electrophoresis or fluoride solutions) by the study of fluoride penetration from amalgams either in dentine or in deep enamel, which are more susceptible to caries than superficial enamel. These experiments give evidence of a fast penetration of fluoride into dental tissues, which may be characterized by an apparent diffusion coefficient of about 10(-10) cm2/s.