Imaging dendritic spines in the hippocampus of a living mouse by 3D-stimulated emission depletion microscopy

Significance

Stimulated emission depletion (STED) microscopy has been used to address a wide range of neurobiological questions in optically well-accessible samples, such as cell culture or brain slices. However, the application of STED to deeply embedded structures in the brain of living animals remains technically challenging.

Aim

In previous work, we established chronic STED imaging in the hippocampus in vivo but the gain in spatial resolution was restricted to the lateral plane. In our study, we report on extending the gain in STED resolution into the optical axis to visualize dendritic spines in the hippocampus in vivo.

Approach

Our approach is based on a spatial light modulator to shape the focal STED light intensity in all three dimensions and a conically shaped window that is compatible with an objective that has a long working distance and a high numerical aperture. We corrected distortions of the laser wavefront to optimize the shape of the bottle beam of the STED laser.

Results

We show how the new window design improves the STED point spread function and the spatial resolution using nanobeads. We then demonstrate the beneficial effects for 3D-STED microscopy of dendritic spines, visualized with an unprecedented level of detail in the hippocampus of a living mouse.

Conclusions

We present a methodology to improve the axial resolution for STED microscopy in the deeply embedded hippocampus in vivo, facilitating longitudinal studies of neuroanatomical plasticity at the nanoscale in a wide range of (patho-)physiological contexts.

Reversing Reactivity: Stereoselective Desulfurative 1,2-trans-O-Glycosylation of Anomeric Thiosugars with Carboxylic Acids under Copper or Cobalt Catalysis

We have discovered a new mode of reactivity of 1-thiosugars in the presence of Cu(II) or Co(II) for a stereoselective O-glycosylation reaction. The process involves the use of a catalytic amount of Cu(acac)₂ or Co(acac)₂ and Ag₂CO₃ as an oxidant in α,α,α-trifluorotoluene. Moreover, this protocol turned out to have a broad scope, allowing the preparation of a wide range of complex substituted O-glycoside esters in good to excellent yields with an exclusive 1,2-trans-selectivity. The late-stage modification of pharmaceuticals by this method was also demonstrated. To obtain a closer insight into the reaction mechanism, cyclic voltammetry was performed.

Prevalence of coeliac disease in diabetic children and their first- degree relatives in west Algeria: screening with serological markers

Atypical and relatively silent forms of coeliac disease (CD) have been described in insulin-dependent diabetes mellitus (IDDM). Our aim was to evaluate the prevalence of CD-IDDM with serological markers and to investigate the presence of CD in the IDDM first-degree relatives. During 1993-94 we explored 116 IDDM patients reported as new cases and 381 first-degree relatives of IDDM patients. Determination of IgA and IgG antigliadin antibodies (AGA) and IgA antiendomysium antibodies (AEA) was made. Jejunal biopsy was performed in symptomatic patients or in those with positive serological markers, (i) Nineteen IDDM-CD were identified and 5 were suspected. Thus, the prevalence of CD in IDDM patients was between 16.4 and 20%. AGA and/or AEA were abnormal in 13 and normal in 5. Sensitivity was 80% for the three tests when used simultaneously and specificity was 100%. (ii) In the family study, 26 sera of asymptomatic first-degree relatives of IDDM patients were positive for at least one of the serological markers; 13 of them had villous atrophy. Systematic serological screening in IDDM allowed us to detect CD and evaluate the true incidence.