Showing papers by "Aix-Marseille University published in 1986"

Experimental autoimmune encephalomyelitis mediated by T lymphocyte lines: genotype of antigen-presenting cells influences immunodominant epitope of basic protein.

Abstract: Lewis rats are susceptible to experimental autoimmune encephalomyelitis (EAE), and their T lymphocytes recognize epitopes in the 68-88 sequence of guinea pig myelin basic protein (BP). BN rats are resistant to EAE, and their T lymphocytes recognize epitopes outside of the 68-88 sequence, probably in the 43-67 portion of BP. To investigate the influence of the genome of antigen-presenting cells (APC) on the dominance of BP epitopes for T lymphocyte lines, we selected anti-BP lines from (Lewis X BN)F1 rats by using the APC of Lewis, BN, or F1 origin. We now report that the F1/Lewis and F1/F1 lines recognized the 68-88 epitopes and were highly encephalitogenic in F1 rats, whereas the F1/BN line recognized the 43-67 epitopes and was only weakly encephalitogenic. Thus, the genotype of the APC can influence the immunologic dominance for T lymphocytes of BP epitopes, and this dominance in turn can influence the expression of disease.

31P nuclear magnetic resonance study of a human colon adenocarcinoma cultured cell line.

Abstract: 31 P nuclear magnetic resonance (NMR) spectroscopy has been used to monitor the energy metabolism in a human colon adenocarcinoma cell line (HT 29). NMR spectra were recorded at 80.9 MHz on approximately 2.5 × 10 8 cells continuously perfused with culture medium within a 20-mm NMR sample tube. Typical NMR spectra display a series of well-resolved resonances assigned to nucleoside triphosphates (mainly adenosine 5′-triphosphate), uridine diphosphohexose derivatives (uridine 5′-diphosphate- N -acetylglucosamine, uridine 5′-diphosphate- N -acetylgalactosamine, uridine 5′-diphosphate-glucose), intra- and extracellular inorganic phosphate, and phosphomonoesters (mainly phosphorylcholine and glucose 6-phosphate). Measurement of phosphorylated metabolite concentrations from the intensity of NMR signals is in good agreement with the results provided by conventional biochemical assays. 31 P NMR allows to follow noninvasively the effect of anoxia on HT 29 cells. The results indicate that the cells are able to maintain about 60% of their initial nucleoside triphosphate level after 2 h of anaerobic perfusion. Cells accumulate inorganic phosphate during anoxia and the intracellular-extracellular pH gradient increases from 0.5 in well-oxygenated cells to more than 1 pH unit under anoxic conditions. The value of intracellular pH of well-oxygenated HT 29 cells is 7.1. The effect of glucose starvation upon energy metabolism has also been examined in real time by NMR: a rapid decline of adenosine 5′-triphosphate down to 10% of the initial value is observed over a period of 2 h. In contrast, the level in uridine diphosphohexoses reaches a new steady state value representing 60% of the initial one. Refeeding the cells with 25 mm glucose leads to a dramatic drop of internal pH reflecting the activation of the glycolytic pathway.

Analytical Electron Microscopy Of Multilayered Thin Films Using Microcleavage

Abstract: Microcleavage transmission electron microscopy (MTEM) has been applied to the study of many properties of multilayered samples. We illustrate the unique capabilities of this technique for obtaining a detailed structural picture of the multilayer in order to study long-range perpendicular thickness drifts, lateral variations, roughness, substrate quality, adherence, thermal stability, composition, and crystallinity.

Information Systems and Scientometric Study in Chemical Oceanography

Abstract: The structure of the scientific information in Marine Chemistry or Chemical Oceanography has been examined, using sample data obtained from Chemical Abstracts. It appears clearly, that these two fields are too isolated, and still too far from the fundamental concerns of other chemists. In the next future, it will be very important to establish various set of standards able to be used in online information retrieval. Among these, the geographical location as Longitude and latitude, and description of the analytical methods used, are the more important. It will be also very useful 1, to use all the capabilities of computer exchanges, to create on an host computer, a databank of characteristic spectra, chromatograms, etc… in this way, all laboratories will have access to the same data, and will be able to use them with their inhouse computer, not only to obtain a paper chart, but to compare, recalibrate, add, substract… these standards from their own results. In this way, the scientific publications in the field of marine sciences, will become really interactive. This will give, by comparison with other areas of science, a definitive advantage to Chemical Oceanography.

Heterocyclic Substituents in SRN 1 Reactions

Abstract: Electron-tranfer substitution reaction (SRN1) is generalized to the heterocyclic electrophile, l-methyl-2-chloromethyl- 5-nitroimidazole, and to the heterocyclic nucleophiles, 3-ethyl-5-nitrotetrahydro-1, 3-oxazine salt and 2, 2-dimethyl-5-nitro-l, 3-dioxane salt. New l-methyl-5-nitroimidazoles bearing a trisubstituted ethylenic double bond in the 2 position are obtained in high yields. Heterocyclic substituents change very little the substitution reaction but increase dramatically the elimination of nitrous acid.

Compounds of Organogallium Anions

Abstract: The compounds in this section are arranged in a way similar to that of the previous sections, i.e., the description begins with tetraorganylgallates, [GaR4]-, and is followed by [GaRnX4-n]- anions (n = 1 to 3) where X stands for hydrogen, halogen, pseudohalogen, oxygen groups, etc. Finally, very extended subsections deal with organogallium pyrazolyl anions bonded to transition metal fragments via the second N atom of pyrazolyl, thus acting as anionic donor ligand with respect to the transition metal. Depending on the type of the transition metal moiety, these compounds may be neutral or ionic.

Organogallium-Phosphorus and -Arsenic Compounds

Abstract: The compounds in this section, listed in Table 71, are of the GaR2ER2’ type (E = P or As, R’ = H only for No. 7), except for No. 6, which contains a Ga(CH3)Cl unit.

Organogallium-Germanium Compounds

Abstract: This compound is formed by decomposition of K[Ga(CH3)2(GeH3)Cl]-1.5CH3OCH2CH2OCH3 (see p. 418) in C6H5CH3 at -15°C over a period of 2 h. Removal of KCl and solvent (pumping at -15°C for 2 d), followed by distillation at 25 to 30°C under high vacuum, yielded a colorless liquid consisting of a mixture of the compound (76%) and Ga(CH3)2H (based on analyses). The products could not be separated because Ga(CH3)2GeH3 decomposes slowly at 25°C to give Ga(CH3)2H and (GeH2)n.

Organogallium-Boron Compounds

Abstract: The compound was first prepared by treating Ga(CH3)3 repeatedly with B2H6 at — 45°C until no further reaction was apparent [1]. In a more recent paper, Ga(CH3)3 was allowed to react with a fivefold excess of B2H6 at -15°C for 3 h and was isolated in a 20 to 42% yield by trap-to-trap distillation of the volatiles in a vacuum system [6]. An 80% yield was obtained from the reaction of Ga(CH3)2Cl with an excess of powdered LiBH4 at -15°C with pumping for 4 h and vacuum fractionation as above. This method was suitable for the preparation of Ga(CH 3 ) 2 BD 4 using LiBD4 [6]. The formation from GaH(BH4)2 and Ga(CH3)3 at -45°C, along with GaH(CH3)BH4, is indicated in a reaction scheme in [5].

Organogallium-Transition Metal Compounds

Abstract: This chapter contains transition metal (M) compounds with Ga-M bonds. Other organogal-lium derivatives of transition metals without such a bond are described in Sections 13.6.2.1 to 13.6.2.4. With organogallium species five types of complexes have been described in the literature. Formula I represents adducts of Ga(C6H5)3 with anionic 18-electron complexes (no adducts with neutral species are known). Compounds with a three-coordinate Ga atom are described with Formulas II and III; the latter complexes have only been identified in solution. Compounds with a four-membered M-Ga-M-Ga ring (Formula IV) are only known as iron carbonyl derivatives and contain one molecule of a base at each Ga atom for stabilization. The base-free derivative of IV (No. 11 in Table 73) was also described but only characterized by IR spectroscopy. Incorporation of N-bases (C5H5N, tetramethylethylenediamine, 2,2′-bipyridyl) causes the molecule to monomerize to give compounds of Formula V, containing a formally “subvalent” Ga atom.

Organogallium-Oxygen Compounds

Abstract: Ga(CH3)2OH can be obtained by distilling Ga(CH3)3-O(C2H5)2 in a vacuum line onto a slight excess of H2O at -196°C and warming the mixture until hydrolysis is proceeding slowly. The rate of reaction can be regulated by controlling the temperature [2]. A checked version of this procedure with an 80% yield, starting with the in situ preparation of the etherate from GaCl3 and LiCH3 in ether at -78°C, is published in [8]. The resulting reaction mixture is allowed to stand at room temperature for 30 min, recooled to -78°C and hydrolyzed by dropwise addition of H2O. The workup involves dissolution of LiCl with H2O at room temperature, separation of the organic phase, evaporation of the solvent in an N2 stream, and recrystallization from petroleum ether [2,8]. The compound is also formed when either tetrameric Ga(CH3)2CN [5] or dimeric Ga(CH3)2P(C6H5)2 [6] is exposed to atmospheric moisture. The electroreduction of CH3I on a Ga cathode in CH3CN-NaClO4 gives the compound in about 35 to 40% yield along with “GaCH3O” [10]. The formation of Ga(CH3)2OH by thermal decomposition of Ga(CH3)2OOCH3 at 120°C in C9H20 [12] and of Ga(CH3)2OOC4H9-t under similar conditions [12,13] is also reported; see pp. 199/200.

Organogallium-Selenium Compounds

Abstract: Ga(CH3)2SeCH3 is obtained as a nonvolatile solid by condensation of Ga(CH3)3 on CH3SeH (1:1 mole ratio). The dimeric product melts at 119 to 120°C. The vapor pressure has been determined in the 120 to 140°C range to give the equation log (p/Torr) = 9.63–3450/T and ?HV=16 kcal/mol. The compound is dimeric in the vapor phase. Above 160°C decomposition occurs with formation of a non-condensable gas. With N(CH3)3 a 1:1 adduct is formed [1].

Organogallium-Sulfur Compounds

Abstract: All compounds with Ga-S a bonds are listed in Table 48. They are mainly thiolates, GaR2SR’, most of them only recently prepared [12, 13]. The other derivatives contain potentially chelating ligands (Nos. 7 to 12 and No. 22), including chelating S N systems where it is impossible to distinguish between covalent and coordinative bonds to either the S or N atom. Derivatives of monothiocarboxylic acids, GaR2OC(S)R’. have already been described with the gallium-oxygen compounds in 5.1.3.2, p. 194. A few adducts are listed at the end of Table 48.

Low-Valence Organogallium Compounds

Abstract: Products of the reaction of Ga(CH2Si(CH3)3)3 with alkali metal hydrides were originally reported to be of the M[Ga(CH2Si(CH3)3)2] type, including a few adducts, and were believed to arise from reductive elimination of Si(CH3)4 from M[Ga(CH2Si(CH3)3)3H] intermediates [1]. But these results could not be reproduced later, and the products were identified as alkali metal compounds of the hydrido anion [Ga(CH2Si(CH3)3)3H]- [2]; see 13.2, p. 320.