High speed atomic force microscopy to investigate the interactions between toxic Aβ1-42 peptides and model membranes in real time: impact of the membrane composition

Due to an aging population, neurodegenerative diseases have become a major health issue, the most common being Alzheimer's disease. The mechanisms leading to neuronal loss still remain unclear but recent studies suggest that soluble Aβ oligomers have deleterious effects on neuronal membranes. Here, high-speed atomic force microscopy was used to assess the effect of oligomeric species of a variant of Aβ1-42 amyloid peptide on model membranes with various lipid compositions. Results showed that the peptide does not interact with membranes composed of phosphatidylcholine and sphingomyelin. Ganglioside GM1, but not cholesterol, is required for the peptide to interact with the membrane. Interestingly, when they are both present, a fast disruption of the membrane was observed. It suggests that the presence of ganglioside GM1 and cholesterol in membranes promotes the interaction of the oligomeric Aβ1-42 peptide with the membrane. This interaction leads to the membrane's destruction in a few seconds. This study highlights the power of high-speed atomic force microscopy to explore lipid-protein interactions with high spatio-temporal resolution.

Interaction of Aβ1-42 peptide or their variant with model membrane of different composition probed by infrared nanospectroscopy

Toxicity of Aβ peptides involved in Alzheimer's disease is linked to the interaction of intermediate species with membranes. Nanoscale Infrared Spectroscopy enhances the study of the morphology and the secondary structure of the peptides as fibers or oligomers interacting with membranes of different compositions, with nanometer scale resolution. Membrane models are used to investigate the role of different lipids in their interactions with Aβ peptides. This work clearly brings to light that the presence of cholesterol in membranes is favorable to the interaction with Aβ peptides in oligomers or aggregates.

[Amebic keratitis]

Amoebic keratitis is an uncommon pathology mainly implicated in eye infection in contact lens wearers. The offending parasite is a free-living amoeba of the genus Acanthamoeba. Diagnosis is often delayed because clinical signs are confusing especially at the onset. Samples for parasitic tests should be taken not only for the infection site but also from the lenses and cleaning products. A standard treatment of amoebic keratitis has not been established. Several drugs are theoretically active but achieve inconsistent results. Recently keratitis has been observed at a seemingly high incidence in developing countries but epidemiologic data is still scarce.

A randomized study of etoposide and carboplatin with or without paclitaxel in the treatment of small cell lung cancer

Small cell lung cancer accounts for 20% to 25% of all lung cancer cases and is initially responsive to combination chemotherapy. However, the majority of patients relapse, and at that point their disease is highly resistant to chemotherapy. The combination of etoposide with either cisplatin or carboplatin is regarded as the standard of care for these patients. Previous studies have documented the activity of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) at doses of 135 to 250 mg/m2 administered over 1, 3, or 24 hours as either a single agent or in combination with etoposide and a platinum compound. Studies adding paclitaxel to etoposide/carboplatin (EP) have demonstrated complete responses in both limited and extensive disease, but all have been in single-arm phase II studies. Preliminary data also suggest the possibility of a dose-response curve for the combination. We recently began a randomized phase II/III comparison of the standard EP to EP plus paclitaxel for newly diagnosed patients with limited or extensive small cell lung cancer. Carboplatin in this study is dosed according to area under the concentration-time curve as calculated by the Calvert formula. The study compares EP (carboplatin area under the concentration-time curve of 6 intravenously [IV] over 30 to 60 minutes on day 1, with etoposide 120 mg/m2 IV days 1 to 3) versus EP plus paclitaxel (paclitaxel 200 mg/m2 IV 1-hour infusion on day 1, carboplatin area under the concentration-time curve of 6 IV over 30 to 60 minutes on day 1, and etoposide 50/100 mg orally on alternating days 1 to 10). The design, inclusion criteria, and staging of patients in this study will be presented with initial accrual and patient characteristics. Randomized studies of this type are essential if the true role of this new combination is to be fully evaluated.

Myopic photorefractive keratectomy in eyes with atypical inferior corneal steepening

PURPOSE

To evaluate the visual and refractive results of photorefractive keratectomy (PRK) in eyes with atypical inferior corneal steepening (AICS).

SETTING

Department of Ophthalmology, Hôpital Morvan, University of Breast, France.

METHODS

Using videokeratopography, we screened 310 eyes that had PRK from November 1992 through November 1993 and found that 35 eyes exhibited topographic patterns consistent with AICS with no clinical findings. The results at 6 months and 1 year were compared with those of 185 eyes with normal topography treated concurrently.

RESULTS

There were no statistically significant differences between the two groups in mean spherical equivalent, mean uncorrected visual acuity, and mean best spectacle-corrected visual acuity 6 months and 1 year after PRK.

CONCLUSION

After 1 year, PRK in eyes with AICS appeared to give results similar to those in eyes with normal topography. Further follow-up is needed.