Solvent tuned single molecule dual emission in protic solvents: effect of polarity and H-bonding.

Phen-PENMe2 has recently been proposed as a promising new molecule displaying solvent-tuned dual emission, highlighting an original and newly-described charge transfer model. The study of the photophysical behaviour of this molecule was extended to include protic solvents. The effects of polarity and hydrogen bonding lead to an even more evident dual emission associated with a large multi-emission band in some solvents like methanol, highlighting Phen-PENMe2 as a promising candidate for white light emission.

The electronic properties of mixed valence hydrated europium chloride thin film.

We investigate the electronic properties of a model mixed-valence hydrated chloride europium salt by means of high resolution photoemission spectroscopy (HRPES) and resonant photoemission spectroscopy (RESPES) at the Eu 3d → 4f and 4d → 4f transitions. From the HRPES spectra, we have determined that the two europium oxidation states are homogeneously distributed in the bulk and that the hydrated salt film is exempt from surface mixed valence transition. From the RESPES spectra, the well separated resonant contributions characteristic of divalent and trivalent europium species (4f(6) and 4f(7) final states, respectively) are accurately extracted and quantitatively determined from the resonant features measured at the two edges. The partial absorption yield spectra, obtained by integrating the photoemission intensity in the valence-band region, can be well reproduced by atomic multiplet calculation at the M(4,5) (3d-4f) absorption edge and by an asymmetric Fano-like shape profile at the N(4,5) (4d-4f) absorption edge. The ratio of Eu(2+) and Eu(3+) species measured at the two absorption edges matches with the composition of the mixed valence europium salt as determined chemically. We have demonstrated that the observed spectroscopic features of the mixed valence salt are attributed to the mixed-valence ground state rather than surface valence transition. HRPES and RESPES spectra provide reference spectra for the study of europium salts and their derivatives.

Solvent-tuned dual emission: a structural and electronic interplay highlighting a novel planar ICT (OPICT).

Displaying a dual emission, a Phen-PENMe2 compound can be foreseen as a new model for fundamental studies. It is based on an excited state cumulene-type structure, involving orthogonal π orbital (OPICT). In contrast to the "Twisted Intramolecular Charge Transfer" (TICT) emission, the OPICT emissive state is planar. This new compound is also a potential candidate for local ratiometric probes of medium polarity (mixture of solvents and biological systems) and white emission.

Novel ruthenium(II) and zinc(II) complexes for two-photon absorption related applications.

Two new fluorene derivatized 1,10-phenanthroline ligands and related tris-chelate Ru(II) or Zn(II) coordination complexes have been synthesised. The linear and nonlinear (two-photon induced fluorescence) photophysical measurements have contributed to highlight the possibility to tune the absorption spectral range and excited lifetime, depending on ligand substitution and nature of the metal. More significantly, the observation of two-photon absorption (TPA) associated with long-lived metal-to-ligand charge-transfer (MLCT) excited states in the Ru(II)-based chromophores, opens a wide range of applications in the near infrared.

On-column refolding of an insoluble histidine tag recombinant exopolyphosphatase from Trypanosoma brucei overexpressed in Escherichia coli.

An exopolyphosphatase gene has been cloned by polymerase chain reaction (PCR) from Trypanosoma brucei and the corresponding protein overexpressed as a recombinant His-tag (histidine tag) exopolyphosphatase in E. coli in order to characterize its biochemical activity and to produce antibody to determine its localization. Because overexpression of this protein in bacteria resulted in the formation of inactive inclusion bodies, these structures were first solubilized in denaturant condition (6 M urea). Secondly, after a capture step using immobilized metal affinity chromatography (IMAC), a gradual refolding of the protein was performed on-column from 6 M to 0 M urea in the presence of 1% Triton X-100. Triton X-100 was used to abolish protein aggregation during the refolding step. The purified enzyme was active, demonstrating that at least part of the proteins was properly refolded.

A novel C-terminal kinesin is essential for maintaining functional acidocalcisomes in Trypanosoma brucei.

Kinesins are cytoskeletal motor proteins that play roles in a variety of fundamental cellular processes including cell division and the anterograde transport of vesicles and organelles. We purified, cloned, and functionally characterized in Trypanosoma brucei a new member of the C-terminal kinesin family, TbKIFC1. Kinetic constants of the recombinant motor domain of TbKIFC1 were estimated at 0.56 microm for the microtubule dissociation constant (K(d)) with a k(cat) of 0.2 s(-1). Immunolocalization analysis showed an association of TbKIFC1 with punctate structures. Because they were rapidly transported to the negative pole of the microtubule after NH(4)Cl treatment, these structures were considered to be associated with acidic vesicles. To determine the role of the kinesin in vivo, we produced an inducible kinesin-deficient strain by double-stranded RNA interference methodology. Mutant cells were loaded with the fluorescent reagent fura2/acetoxymethylester to measure intracellular free calcium ([Ca(2+)](i)). The resting [Ca(2+)](i) was unchanged in mutant cells; however, alkalinization of acidic vesicles induced by NH(4)Cl or nigericin was not followed by release of Ca(2+). These data and the relative importance of the ionomycin-releasable and the ionomycin-plus-NH(4)Cl-releasable Ca(2+) pools suggest a lower Ca(2+) content in acidocalcisomes and dysfunctional Ca(2+) release.

Sleep abnormalities with REM disorder in experimental Creutzfeldt-Jakob disease in cats: a new pathological feature.

Alterations in sleep organization were studied during the clinical phase of experimental Creutzfeldt-Jakob disease (CJD) in cats. Twenty months after intracerebral inoculation of a CJD agent, cats developed clinical signs including behavioral changes, diminished grooming activity, dysmetria, startle reflex, myoclonus, and unusual sleep abnormalities. Rapid eye movement (REM) sleep displayed a new and irreversible organization, with a continuous and constant pseudoperiodic pattern of rapid eye movements, synchronous with diffuse bursts of cortical abnormalities and with ponto-geniculo-occipital (PGO) wave activity. Computer analysis revealed a constant morphology of cortical bursts and their temporal relationship with ocular episodes. Induction of PGO wave activity with benzoquinolizine derivative Ro 4-1284 demonstrated the PGO-dependent nature of the cortical alterations. Abnormal unresponsive states were observed during REM sleep phases and arousal thresholds were increased in CJD cats during REM sleep. The percentages of wakefulness and slow-wave sleep were reversed in these animals. Preliminary neuropathological observations included discrete to minimal spongiosis of cerebral gray matter and a remarkably focalized intracytoplasmic vacuolation in neurons of the raphé system. Our findings suggest that particular neuronal systems involved in sleep regulation are impaired in CJD cats.

Modulation of the number of muscarinic receptors in mouse neuroblastoma cells by soman.

Long-term preincubation at 37 degrees of mouse neuroblastoma cells (clones NS-20 and N1E-115) with soman, a potent and irreversible cholinesterase inhibitor, resulted in a significant decrease in the number of [3H]N-methylscopolamine binding sites and in the inhibition of carbamylcholine-induced cyclic GMP formation. The disappearance of surface muscarinic receptors and the desensitization of the receptor-mediated response seem to occur via accumulation of acetylcholine in the culture medium. The significance of these findings is discussed.

Histological and histochemical changes in the central nervous system of the rat poisoned by an irreversible anticholinesterase organophosphorus compound.

The effect of soman, a powerful organophosphorus (OP) cholinesterase inhibitor, was investigated in the central nervous system (CNS) of Wistar rats by neurohistology, histochemical mapping of acetylcholinesterase (AChE), and biochemical determination of cholinesterase (ChE) activity. Rats were poisoned by one lethal or sublethal subcutaneous (s.c.) injection or by several less strong weekly doses. When the acute cholinergic action of the OP led to severe respiratory failure and to repeated or prolonged convulsions, the surviving rats exhibited neuronal changes similar to those of hypoxic encephalopathy. In one case chronic intoxication gave rise to these symptoms and lesions after the fourth injection. The histochemical data showed that lesioned gray structures were generally poor in AChE. The enzymatic inhibition was quick and strong, but differed from one structure to another. ChE recovery was rapid until about 96 h after poisoning, the time course depending on the structure, but was incomplete even after 8 days. An attempt to correlate the initial level of ChE inhibition with the severity of the symptoms was not very conclusive. Our data suggest that the encephalopathy comes at least in part from complex hypoxic factors produced by the cholinergic crisis. The sequelae of slight hypoxic encephalopathy could account for some nervous long-term effects in men acutely poisoned by OP and surviving owing to mechanical ventilation.

["In vitro" interactions between influenza virus and mouse lung alveolar macrophages (author's transl)]. / Interactions entre le virus grippal et le macrophage alvéolaire de souris: étude in vitro.

Interactions between influenza virus A/PR/8/34 (H0N1) and Balb/c mouse lung alveolar macrophages have been studied in vitro. One day after initiation of alveolar macrophage culture in 35 mm Falcon dishes, the virus suspension was allowed to adsorb to the cells for 1 h. Detachment of cells from the plastic substrate, morphological changes in adherent cells and decreased phagocytosis of heat-killed Candida albicans occured slowly as compared to control cultures. These facts appeared to be directly correlated to the concentration of viruses in the inoculum. Data yielded by virus titrations, electron microscopy and immunofluorescence suggest that mouse lung alveolar macrophages are able to take up a large amount of viral particles and inhibit their replication, allowing only an abortive viral cycle.

[Morphometric study of the bronchopulmonary lymphoid system in the normal mouse and the mouse infected with influenza virus]. / Etude morphométrique du système lymphoïde bronchopulmonaire de la souris normale et de la souris infectée par le virus grippal.

Morphometric study of mouse bronchus-associated lymphoid tissue (BALT) using an image analyser and histological sections at close and regular intervals was carried out in lungs of control and influenza infected mice two to three months old. The mean area of BALT did not reach 0,1 p. 100 of the whole mean area of examined lung sections in control mice; this percentage was significantly greater one month after primary exposure to influenza virus.

[Pinguecula and pterygium: histologic and electron microscopic study (author's transl)]. / Pinguecula et pterygion: étude histopathologique et ultrastructurale.

Two pingueculae combined with pterygia were studied by light and electron microscopy. Hyaline degeneration of the collagen, dark staining granular, von Kossa negative concretions and elastotic material were observed in both conditions together with marked changes in the fibroblasts, endothelial cells, pericytes and the basement membrane of conjunctival capillaries and small veins. The elastotic material is similar to that observed in solar elastosis, where the collagen fibers are less severely damaged. Chronic sun exposure of the pericorneal conjunctiva may damage endothelial cells primarily and disturb vascular exchanges. This would result in accelerated degeneration and regeneration of endothelial cells, in thickening of the basement membrane and, secondarily, disturbed metabolism of fibroblasts with alterations of the collagen and elastic fibers.

[Bronchopulmonary lymphocytes and their B and T subpopulations in control and experimental influenza infected mice]. / Lymphocytes bronchopulmonaires et leurs sous-populations B et T chez des souris normales et des souris soumises à une grippe expérimentale.

Immunofluorescent studies showed that, whereas the total number of lymphocytes was still increased on the third and fourth weeks of experimental airborne influenza, the B/T cell ratio remained in the same range as in control animals. This ratio is comparable to results with mouse peripheral lymph nodes.

[Local immune response in mouse experimental airborne influenza: immunoglobulin concentrations, antibody levels of immunoglobulin classes and anamnestic response in bronchial washings (author's transl)]. / La réponse immunitaire locale au cours de la grippe expérimentale de la souris: immunoglobulines, anticorps spécifiques et réponse anammestique des sécrétions bronchiques

Sera and bronchial washings from normal mice and from mice previously infected with influenza virus were analyzed for their concentration of four immunoglobulin (Ig) classes by the method of single radial immunodiffusion and for their content of specific antibody of these Ig classes by the immunofluorescent method. IgA were not detected in bronchial washings from normal mice. The IgA/IgG ratio was not higher than 0.33 in infected mice. The IgA level increased briefly in infected bronchial washings, but the levels of IgG2 and particularly of IgG1 exhibited a longer and higher increase. The maximal increase of these three Ig classes occurred by the seventh day and might have derived from transsudated serum. IgM was not identified in normal bronchial washings, but immunofluorescence detected IgM in infected washings, which also showed specific antibody in each of the four Ig classes. IgG2 and IgM contained antibody in greatest, IgA in lower concentration. Our results indicate that the most part of bronchial antibody was produced locally, since the ratio of Ig concentration to antibody titre of each Ig class was consistently higher for bronchial washings than for sera. An anamnestic secretory antibody response could not be demonstrated in bronchial washings.

[Bronchioloalveolar metaplasia during experimental influenza in mice--histological and ultrastructural study]. / La métaplasie bronchioloalvéolaire au cours de la grippe experimentale de la souris - etude histologique et ultrastructurale

Squamous and "adenomatous" metaplastic changes which developed in the lungs of mice during the healing phase of experimental influenza were studied by histology and electron microscopy. The squamous nests contained epithelial cells possessing bundles of tonfibrils and being similar to bronchial basal cells. The "adenomatous" cavities were lined, either by cells related to Clara cells or by basal type-cells, which underlined cells related to Clara cells. A local and transitory hyperplasia of type II pneumocytes occurred by the third week. Both kinds of metaplasia seemed to proceed from the bronchial or bronchiolar epithelium. The adenomatous cavities might partly result from progressive differentiation of squamous epithelial cells into cells of glandular type. A ten-month long histologic survey failed to exhibit carcinomatous transformation of metaplasia. Pleiomorphism of influenza regenerative metaplasia might arise from extensive and severe epithelial changes involving all levels of the lower respiratory tract. Such a long persistence of metaplastic changes remains unexplained.