[Experience of a care pathway for psychological and behavioral symptoms of dementia]. / Expérience d'un parcours de soins des symptômes psychologiques et comportementaux des démences.

Behavioral and psychological symptoms of dementia (BPSD) are present in more than eighty percent of patients, resulting in a significant decrease of quality of life of patients and caregivers. To provide the most appropriate and early response to behavioral disorders, a specific care pathway, unique in France, has been created within the Memory Center at the Hospices Civils of Lyon. It includes a consultation "Behavior" aimed to intervention and guidance, a Cognitive-Behavioral Unit for pharmacological and non-pharmacological interventions in a comprehensive care of the patient during 3 to 4 weeks, and an Alzheimer's disease mobile team, which can assess the BPSD in the patient's living environment at home or in nursing homes, appraise drug treatments and environment, and give training for caregivers. This care pathway is aimed to provide individualized and early care for behavioral crises secondary prevention, taking into account the psychological, neuropsychological and somatic context of the behavioral disorders occurrence.

Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus.

The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O(2) tension is reduced. The cbb(3) and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O(2) pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb(3)(-) mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O(2)-detoxifying action of terminal oxidases.

Organization and expression of photosynthesis genes and operons in anoxygenic photosynthetic proteobacteria.

Genes belonging to the same metabolic route are usually organized in operons in microbial genomes. For instance, most genes involved in photosynthesis were found clustered and organized in operons in photosynthetic Alpha- and Betaproteobacteria. The discovery of Gammaproteobacteria with a conserved photosynthetic gene cluster revives the questions on the role and the maintenance of such organization in proteobacteria. In this paper, we report the analysis of the structure and expression of the 14 kb cluster (crtEF-bchCXYZ-pufBALMC-crtADC) in the photosynthetic betaproteobacterium Rubrivivax gelatinosus, with the purpose of understanding the reasons and the biological constraints that might have led to the clustering of photosynthesis genes. The genetic analyses are substantiated by reverse transcription-PCR data which reveal the presence of a transcript encompassing the 14 genes and provide evidence of a polycistronic 'super-operon' organization starting at crtE and ending 14 kb downstream at the crtC gene. Furthermore, genetic analyses suggest that one of the selection pressures that may have driven and maintained the photosynthesis operons/super-operons in proteobacteria could very likely be the coexpression and regulation of the clustered genes/operon.

Global regulation of photosynthesis and respiration by FnrL: the first two targets in the tetrapyrrole pathway.

Fnr is a regulator that controls the expression of a variety of genes in response to oxygen limitation in bacteria. To assess the role of Fnr in photosynthesis in Rubrivivax gelatinosus, a strain carrying a null mutation in fnrL was constructed. It was unable to grow anaerobically in the light, but, intriguingly, it was able to produce photosynthetic complexes under high oxygenation conditions. The mutant lacked all c-type cytochromes normally detectable in microaerobically-grown wild type cells and accumulated coproporphyrin III. These data suggested that the pleiotropic phenotype observed in FNR is primarily due to the control at the level of the HemN oxygen-independent coproporphyrinogen III dehydrogenase. hemN expression in trans partially suppressed the FNR phenotype, as it rescued heme and cytochrome syntheses. Nevertheless, these cells were photosynthetically deficient, and pigment analyses showed that they were blocked at the level of Mg(2+)-protoporphyrin monomethyl ester. Expression of both hemN and bchE in the FNR mutant restored synthesis of Mg(2+)-protochlorophyllide. We, therefore, conclude that FnrL controls respiration by regulating hemN expression and controls photosynthesis by regulating both hemN and bchE expression. A comprehensive picture of the control points of microaerobic respiration and photosynthesis by FnrL is provided, and the prominent role of this factor in activating alternative gene programs after reduction of oxygen tension in facultative aerobes is discussed.

Characterization of the core complex of Rubrivivax gelatinosus in a mutant devoid of the LH2 antenna.

The core complex of purple bacteria is a supramolecular assembly consisting of an array of light-harvesting LH1 antenna organized around the reaction center. It has been isolated and characterized in this work using a Rubrivivax gelatinosus mutant lacking the peripheral LH2 antenna. The purification did not modify the organization of the complex as shown by comparison with the intact membranes of the mutant. The protein components consisted exclusively of the reaction center, the associated tetraheme cyt c and the LH1 alphabeta subunits; no other protein which could play the role of pufX could be detected. The complex migrated as a single band in a sucrose gradient, and as a monomer in a native Blue gel electrophoresis. Comparison of its absorbance spectrum with those of the isolated RC and of the LH1 antenna as well as measurements of the bacteriochlorophyll/tetraheme cyt c ratio indicated that the mean number of LH1 subunits per RC-cyt c is near 16. The polypeptides of the LH1 antenna were shown to present several modifications. The alpha one was formylated at its N-terminal residue and the N-terminal methionine of beta was cleaved, as already observed for other Rubrivivax gelatinosus strains. Both modifications occurred possibly by post-translational processing. Furthermore the alpha polypeptides were heterogeneous, some of them having lost the 15 last residues of their C-terminus. This truncation of the hydrophobic C-terminal extension is similar to that observed previously for the alpha polypeptide of the Rubrivivax gelatinosus LH2 antenna and is probably due to proteolysis or to instability of this extension.

Involvement of the C-terminal extension of the alpha polypeptide and of the PucC protein in LH2 complex biosynthesis in Rubrivivax gelatinosus.

The facultative phototrophic nonsulfur bacterium Rubrivivax gelatinosus exhibits several differences from other species of purple bacteria in the organization of its photosynthetic genes. In particular, the puc operon contains only the pucB and pucA genes encoding the beta and alpha polypeptides of the light-harvesting 2 (LH2) complex. Downstream of the pucBA operon is the pucC gene in the opposite transcriptional orientation. The transcription of pucBA and pucC has been studied. No pucC transcript was detected either by Northern blotting or by reverse transcription-PCR analysis. The initiation site of pucBA transcription was determined by primer extension, and Northern blot analysis revealed the presence of two transcripts of 0.8 and 0.65 kb. The half-lives of both transcripts are longer in cells grown semiaerobically than in photosynthetically grown cells, and the small transcript is the less stable. It was reported that the alpha polypeptide, encoded by the pucA gene, presents a C-terminal extension which is not essential for LH2 function in vitro. The biological role of this alanine- and proline-rich C-terminal extension in vivo has been investigated. Two mutants with C-terminal deletions of 13 and 18 residues have been constructed. Both present the two pucBA transcripts, while their phenotypes are, respectively, LH2+ and LH2-, suggesting that a minimal length of the C-terminal extension is required for LH2 biogenesis. Another important factor involved in the LH2 biogenesis is the PucC protein. To gain insight into the function of this protein in R. gelatinosus, we constructed and characterized a PucC mutant. The mutant is devoid of LH2 complex under semiaerobiosis but still produces a small amount of these antennae under photosynthetic growth conditions. This conditional phenotype suggests the involvement of another factor in LH2 biogenesis.

Characterization of unusual hydroxy- and ketocarotenoids in Rubrivivax gelatinosus: involvement of enzyme CrtF or CrtA.

Carotenoids are widely spread terpenoids found in photosynthetic organisms and a number of non-photosynthetic fungi and bacteria. The photosynthetic non-sulfur purple bacterium Rubrivivax gelatinosus produces carotenoids by both the spheroidene and the normal spirilloxanthin pathways. The characteristics of two carotenogenesis enzymes, spheroidene monooxygenase CrtA and O-methyltransferase CrtF, were investigated. Disruption of the corresponding genes by insertional mutagenesis affected carotenoid species in both pathways, and the genetic evidence indicated that both genes are involved in the two pathways. In these mutants, several unusual hydroxy- and ketocarotenoids were identified by spectroscopic and chemical methods. Moreover, the carotenoid analyses demonstrated that a large number of different carotenoid intermediates are accepted as substrates by the CrtA enzyme. The combined manipulation of crtF and crtA allowed new carotenoids to be produced and broadened the diversity of structurally different carotenoids synthesized by Rvi. gelatinosus. Methylated carotenoids, such as spheroidene and spirilloxanthin, are known to function as accessory pigments in the light-harvesting and reaction-center complexes of purple bacteria; the demethylated carotenoids described here were able to fulfill the same functions in the mutants.

Rubrivivax gelatinosus acsF (previously orf358) codes for a conserved, putative binuclear-iron-cluster-containing protein involved in aerobic oxidative cyclization of Mg-protoporphyrin IX monomethylester.

This study describes the characterization of orf358, an open reading frame of previously unidentified function, in the purple bacterium Rubrivivax gelatinosus. A strain in which orf358 was disrupted exhibited a phenotype similar to the wild type under photosynthesis or low-aeration respiratory growth conditions. In contrast, under highly aerated respiratory growth conditions, the wild type still produced bacteriochlorophyll a (Bchl a), while the disrupted strain accumulated a compound that had the same absorption and fluorescence emission spectra as Mg-protoporphyrin but was less polar, suggesting that it was Mg-protoporphyrin monomethylester (MgPMe). These data indicated a blockage in Bchl a synthesis at the oxidative cyclization stage and implied the coexistence of two different mechanisms for MgPMe cyclization in R. gelatinosus, an anaerobic mechanism active under photosynthesis or low oxygenation and an aerobic mechanism active under high-oxygenation growth conditions. Based on these results as well as on sequence analysis indicating the presence of conserved putative binuclear-iron-cluster binding motifs, the designation of orf358 as acsF (for aerobic cyclization system Fe-containing subunit) is proposed. Several homologs of AcsF were found in a wide range of photosynthetic organisms, including Chlamydonomas reinhardtii Crd1 and Pharbitis nil PNZIP, suggesting that this aerobic oxidative cyclization mechanism is conserved from bacteria to plants.

Oligomeric state of the light-harvesting complexes B800-850 and B875 from purple bacterium Rubrivivax gelatinosus in detergent solution.

Molecular weights of the purified light-harvesting complexes B800-850 and B875 from purple bacterium Rubrivivax gelatinosus were determined in detergent solutions by analytical centrifugation. The precise density measurement of the antenna solutions provided the values of the buoyant factor of both complexes. Phospholipid content was measured in both antennae. Sedimentation velocity and equilibrium centrifugation indicated that the B800-850 sample is monodisperse and composed from heptamers (α/ß/3 Bacteriochlorophyll α 1.3 Carotenoid)7. B875 is not monodisperse but analysis of equilibrium centrifugation indicated that its smallest oligomer is a dodecamer (α/ß/2 BChlα/2 hydroxyspheroidene)12; larger oligomers probably coexist. The amount of bound detergent could be calculated. B800-850 binds about 0.4-0.5 g of lauryl-dimethyl-amine oxide per g of protein (i.e., 28-35 detergent molecules per α ß ) while a large amount of detergent (2.3 g of decanoylsucrose per g of protein, i.e., 64 detergent molecules per α ß ) is bound to 13875. The electron microscopy images of both antennae in detergent solutions after negative staining are presented and compared to the centrifugation results.