Magnetic Circular Dichroism of Naphthalene Derivatives: A Coupled Cluster Singles and Approximate Doubles and Time-Dependent Density Functional Theory Study.

The UV-vis absorption and magnetic circular dichroism spectra of naphthalene and some of its derivatives have been simulated at the Coupled Cluster Singles and Approximate Doubles (CC2) level of theory, and at the Time-Dependent Density Functional Theory (TD-DFT) level using the B3LYP and CAM-B3LYP functionals. DFT and CC2 predict in general opposite energetic ordering of the Lb and La transitions (in gas phase), as previously observed in adenine. The CC2 simulations of UV and MCD spectra show the best agreement with the experimental data. Analysis of the Cartesian components of the electric dipole transition strengths and the magnetic dipole transition moment between the excited states have been considered in the interpretation of the electronic transitions and the Faraday B term inversion among the naphthalene derivatives.

Highly conserved bifidobacteria in the human gut: Bifidobacterium longum subsp. longum as a potential modulator of elderly innate immunity.

Aging is a physiological and immunological process involving the deterioration of human health, characterised by the progressive alteration of organs and their functions. The speed and extent of such decline are dependent on lifestyle, environment, and genetic factors. Moreover, with advancing age, humans become progressively more fragile and prone to acute and chronic diseases. Although the intestinal microbiota is predisposed to perturbations that accompany aging and frailty, it is generally accepted that the gut microbiota engages in multiple interactions that affect host health throughout the host life span. In the current study, an exhaustive in silico investigation of gut-associated bifidobacteria in healthy individuals from birth to old age revealed that Bifidobacterium longum subsp. longum is the most prevalent member, especially during infancy and in centenarians. Moreover, B. longum subsp. longum genome reconstruction and strain tracing among human gut microbiomes allowed the identification of prototypes of this taxon in the human gut microbiota of healthy elderly individuals. Such analyses guided culturomics attempts to isolate B. longum subsp. longum strains that matched the genomic content of B. longum subsp. longum prototypes from healthy elderly individuals. The molecular effects of selected B. longum subsp. longum strains on the human host were further investigated using in vitro microbe-host interactions, revealing differences in the host immune system transcriptome, with a reduction in gene expression of inflammation-related cytokines. These intriguing findings support the potential anti-aging effects of elderly associated prototypes of B. longum subsp. longum.

Coil-to-globule transition of poly(N-isopropylacrylamide) doped with chiral amino acidic comonomers.

By combined light scattering and circular dichroism measurements (CD), we have investigated the coil-to-globule transition of the thermosensitive polymer poly(N-isopropylacrylamide) (pNIPAAm) copolymerized with a 1/10 fraction of valine- or leucine-derived groups randomly positioned along the chains. The comonomers provide the pNIPAAm chains with chirality, electric charge, and increased hydrophobicity. For valine-derived copolymers, the coil-globule transition is basically unmodified with respect to pNIPAAm, whereas doping with leucine-derived groups significantly lowers the transition temperature and makes the transition discontinuous. We find the CD signal of the chiral comonomers to cleanly depend on the local chain density. We interpret this behavior as an effect of the whole chain conformation on the conformations accessible to the chiral groups.

Investigations on the mobility of the glycosidic linkage in sucrose by study of the phase space structure of a two-degrees of freedom model.

Using the theoretical Ramachandran (phi, psi) maps reported in the literature for sucrose in vacuo and in aqueous solution, we constructed a two-degrees of freedom model in which the glucose and fructose units are substituted by pseudo-atoms. The complete dynamics of this model is studied numerically at fixed energies. Use is made of the graphic method of the Poincaré surfaces of section in phase space and of the Lissajous maps in configuration space. The reduction to just two degrees of freedom allows one to deal with all initial conditions in phase space, whereas the results of molecular dynamics calculations with all internal degrees of freedoms and with the explicit consideration of solvent molecules are taken into account via effective kinetic and potential energy terms. The conformational isomerization mechanism is investigated by singling out the most reactive trajectories in phase space that are associated with the so-called reactive islands and with the resonances found between the phi and psi motions.

Theoretical and experimental studies for the interpretation of vibrational circular dichroism spectra in the CH-stretching overtone region

Two theoretical models for the interpretation of the existing data of CH-stretching overtones' vibrational circular dichroism data are presented. The first model is based on the quantum mechanical Van Vleck contact transformation theory and is applied to the full vibrational problem, the second is based on classical trajectories calculations, by which we treat a simplified three-degrees of freedom Hamiltonian. The latter allows one to derive a qualitative but efficacious picture of the behavior of coupled anharmonic oscillators. In this framework, we analyze the Poincare Surfaces of Section, and calculate the Fourier Cross Spectra of coupled CH-stretchings. Values for the harmonic frequencies and anharmonicities are derived from absorption spectra in the near infrared on partially deuterated compounds. The effect of large amplitude, low-frequency puckering or twisting modes on the ensemble of coupled CH-stretching is taken into account. Copyright 2000 Wiley-Liss, Inc.

Giant spinal extradural cyst.

A case of giant extradural cyst in a 13-year-old girl is described. The cyst was formed by the arachnoid membrane which extruded through a wide lumbar dural defect. It extended from the midthoracic region down to the sacral canal. At operation a large portion of the cystic wall was removed, but the dural defect was not repaired. Two spino-peritoneal shunts were left in place to drain both the intradural and the extradural spaces. The treatment has proved successful during the 20 months that the patient has been observed.

[Kyphotic paraplegia treated by antero-lateral transthoracic decompression and double autograft]. / Paraplégie cyphotique traitée par décompression antéro-latérale transthoracique et double autogreffe

The authors describe a case of malformative kyphosis with paraplegia, treated by transthoracic antero-lateral decompression and anterior spinal fusion by posterior spinal fusion six weeks later. The result of the surgical treatment has been excellent with complete functional recovery. The spinal fusion seems to be the main element of the treatment, by contrast it is impossible to assess the role played by the antero-lateral decompression.

Energy metabolism of isolated rat thymus cells.

The energy metabolism of rat thymus cells has been investigated using preparations of isolated cells obtained by mechanical treatment of whole organs. The addition of glycolytic substrates such as glucose, pyruvate and lactate stimulates the endogenous respiration of these cells by 50%. On the other hand, succinate, glutamate and malate do not produce any effect. Oligomycin (10 mug/ml) inhibits both endogenous and glucose stimulated respiration by about 40%; 2, 4-DNP (50 muM) increases by 100% glucose induced respiration. The results obtained by using mitochondrial and glycolytic inhibitors as well as aminoxyacetic acid (AOA) and following pyridine nucleotides redox changes, support the idea that in thymus cells glucose is able to induce a great enhancement of O2 consumption both by raising the level of endogenous pyruvate and feeding the mitochondrial respiratory chain with cytosolic reducing equivalents, through an active malate-aspartate shuttle. Thymus cells exhibit a high Pasteur effect (74%). Both AOA and 2,4 DNP are able to stimulate aerobic lactate accumulation by 200% and 100% respectively, indicating that either the redox or phosphate potential do influence the rate of aerobic glycolysis in isolated thymus cells. Similar experiments are also reported on other cells with well known biochemical characteristics.

Influence of cefotaxime on Staphylococcus aureus with respect to their interaction with macrophages.

Many antibiotics in addition to their direct effect on bacteria can modulate host defence in different ways. The influence of cefotaxime on the phagocytic and bactericidal activity of mouse peritoneal macrophages was investigated. At concentrations of half the MIC the antibiotic caused macrophages to kill intracellular Staphylococcus aureus at a higher level than did macrophages without drug. Bacteria pretreated with cefotaxime became more sensitive to macrophage phagocytic and bactericidal activity. Macrophages taken from mice receiving intravenous cefotaxime showed greater phagocytic capacity than those from control mice.