MFGE8 does not influence chorio-retinal homeostasis or choroidal neovascularization in vivo

Purpose: Milk fat globule-epidermal growth factor-factor VIII (MFGE8) is necessary for diurnal outer segment phagocytosis and promotes VEGF-dependent neovascularization. The prevalence of two single nucleotide polymorphisms (SNP) in MFGE8 was studied in two exsudative or “wet” Age-related Macular Degeneration (AMD) groups and two corresponding control groups. We studied the effect of MFGE8 deficiency on retinal homeostasis with age and on choroidal neovascularization (CNV) in mice. Methods: The distribution of the SNP (rs4945 and rs1878326) of MFGE8 was analyzed in two groups of patients with “wet” AMD and their age-matched controls from Germany and France. MFGE8-expressing cells were identified in Mfge8+/− mice expressing ß-galactosidase. Aged Mfge8+/− and Mfge8−/− mice were studied by funduscopy, histology, electron microscopy, scanning electron microscopy of vascular corrosion casts of the choroid, and after laser-induced CNV. Results: rs1878326 was associated with AMD in the French and German group. The Mfge8 promoter is highly active in photoreceptors but not in retinal pigment epithelium cells. Mfge8−/− mice did not differ from controls in terms of fundus appearance, photoreceptor cell layers, choroidal architecture or laser-induced CNV. In contrast, the Bruch's membrane (BM) was slightly but significantly thicker in Mfge8−/− mice as compared to controls. Conclusions: Despite a reproducible minor increase of rs1878326 in AMD patients and a very modest increase in BM in Mfge8−/− mice, our data suggests that MFGE8 dysfunction does not play a critical role in the pathogenesis of AMD

tRNA structural and functional changes induced by oxidative stress

Oxidatively damaged biomolecules impair cellular functions and contribute to the pathology of a variety of diseases. RNA is also attacked by reactive oxygen species, and oxidized RNA is increasingly recognized as an important contributor to neurodegenerative complications in humans. Recently, evidence has accumulated supporting the notion that tRNA is involved in cellular responses to various stress conditions. This review focuses on the intriguing consequences of oxidative modification of tRNA at the structural and functional level

Un bébé pleure. Violence et délinquance dans la famille

International audienc

Tolerance to Osmotic Shocks in Rats Kidney Cortex and Medulla

Kidney medulla cells of mammals have to cope with large changes in environmental osmolarity, a challenge most other mammalian cells never have to experience. In these last cells, application of osmotic shocks induces dramatic modifications in chromatin organization. The present paper reports on the changes of medulla cell chromatin in situ, in rat kidney slices submitted to osmotic challenges and in vitro, on preparations of extracted chromatin submitted to changes in environmental ion concentrations. Our results show that the chromatin of kidney medulla cells: (1) does not behave differently from the other mammalian chromatins when submitted in situ or in vitro to osmotic challenges; (2) presents in vitro physico-chemical characteristics similar to those of the other mammalian chromatins; and (3) is protected in vitro, as the other mammalian chromatins, from the disrupting effects of increases in inorganic ion concentrations by different compensatory organic solutes. The ability of kidney medulla cells to adapt to large increases in osmolarity could thus be related to a rapid control of the level of such compounds rather than to some rather specific, intrinsic molecular adaptations of macromolecules

Increased concanavalin A-binding capacity of immunoglobulin G purified from sera of patients with rheumatoid arthritis.

A solid phase radioimmunoassay was set up for direct measurement of the binding capacity of human IgG to three lectins recognizing different carbohydrates of the Fc domain, i.e. peanut agglutinin (PNA), Concanavalin A (Con A) and pokeweed mitogen (PWM) which mainly bind to beta-galactose, alpha-mannose and dimers of N-acetyl-beta-glucosamine respectively. The mean specific binding of the 96 normal IgG tested to PNA and to PWM was statistically higher (P less than 0.001) than that to Con A, whereas no significant differences were observed between the mean specific bindings to PNA and to PWM. A statistically significant linear negative correlation could be established only between the relative bindings (expressed in percentage of the total binding to the three lectins) to PNA and to PWM (r = -0.65, P less than 0.001). The mean specific binding of IgG purified from 34 patients suffering from rheumatoid arthritis (RA) to PNA and to Con A was statistically higher (P less than 0.001) than that reached with PWM, whereas no significant differences were noted between their mean binding capacities to PNA and to Con A. When compared to normal IgG, only four out of 34 RA IgG exhibited a significantly higher binding capacity to PNA, whereas all but one RA IgG possessed a significantly higher binding capacity to Con A. Accordingly, the mean specific binding of RA IgG to Con A was significantly higher than that of normal IgG (P less than 0.001). Besides (and contrary to normal IgG), a statistically significant negative linear correlation was noted between the relative bindings of RA IgG to PNA and to Con A (r = -0.89, P less than 0.001). All the five RA IgG tested exhibited an abnormal circular dichroism. Our data suggest that, by altered steric conformation and glycosylation, mannosyl-residues of RA IgG become prominent or terminal or both, and are therefore able to react more effectively with Con A than normal IgG do

The superstructure of chromatin and its condensation mechanism

Comparison between the internucleosomal distance found by X-ray solution scattering for chicken erythrocyte (23 nm) and sea urchin (30 nm) chromatin indicates that this distance is proportional to the linker length. The diameter of the condensed sea urchin chromatin fibers is about 45 nm which is significantly larger than in chicken erythrocyte chromatin (35 nm). Trivalent cations (Gd, Tb, Cr) and the polyamines spermine and spermidine were found to induce compaction at much lower concentrations than the divalent cations but Gd, Tb and Cr induce aggregation before full compaction of the fibers. The influence of hydrogen bonding is illustrated by comparison of the effects of NaCl, ammonium chloride and alkylammonium chlorides on condensation. Solubility experiments indicate that there is a nearly linear dependence of the Mg-- concentration at which precipitation occures on chromatin concentration and confirm the differences between cations observed by X-ray scattering.The chicken erythrocyte chromatin samples were further characterized by their reduced electric dichroism. The values found are consistent with the model derived from X-ray scattering and are compared with those reported in the literature

The superstructure of chromatin and its condensation mechanism

Electric dichroism and X-ray scattering measurements on solutions of uncondensed and condensed chicken erythrocyte chromatin were interpreted on the basis of model calculations. Information about the state of uncondensed fibers in the conditions of electric dichroism measurements was obtained from scattering patterns recorded as a function of pH, in the presence of spermine and at very low monovalent cation concentrations. Electric dichroism measurements on a complex of uncondensed chromatin with methylene blue were made to determine the contribution of the linker and of the nucleosomes to the total dichroism.A new approach to calculate the dichroism from realistic structural models, which also yields other structural parameters (radius of gyration, radius of gyration of the cross-section, mass per unit length) was used. Only a restricted range of structures is simultaneously compatible with all experimental results. Further, it is shown that previous interpretations of dichroism measurements on chromatin were in contradiction with X-ray scattering data and failed to take into account the distribution of orientation of the nucleosomes in the fibers. When this is done, it is found that the linker DNA in chicken erythrocyte and sea urchin chromatin must run nearly perpendicularly to the fibre axis. Taken together with the dependence of the fibre diameter on the linker length, these results provede the strongest evidence hitherto available for a model in which the linker crosses the central part of the fibre

Electric field x-ray scattering measurements on tobacco mosaic virus

The feasibility of electric field x-ray solution scattering with biological macromolecules was investigated. Electric field pulses (1.25 to 5.5 kilovolts per centimeter) were used to orient tobacco mosaic virus in solution (4.5 milligrams per milliliter). The x-ray scattering is characteristic of isolated oriented particles. The molecular orientation and its field-free decay were monitored with a time resolution of 2 milliseconds by means of synchrotron radiation and a multiwire proportional area detector. The method should also be applicable to synthetic polymers and inorganic colloids