TY  - JOUR
A1  - Capetian, Philipp
A1  - Müller, Lorenz
A1  - Volkmann, Jens
A1  - Heckmann, Manfred
A1  - Ergün, Süleyman
A1  - Wagner, Nicole
T1  - Visualizing the synaptic and cellular ultrastructure in neurons differentiated from human induced neural stem cells - an optimized protocol
JF  - International Journal of Molecular Sciences
N2  - The size of the synaptic subcomponents falls below the limits of visible light microscopy. Despite new developments in advanced microscopy techniques, the resolution of transmission electron microscopy (TEM) remains unsurpassed. The requirements of tissue preservation are very high, and human post mortem material often does not offer adequate quality. However, new reprogramming techniques that generate human neurons in vitro provide samples that can easily fulfill these requirements. The objective of this study was to identify the culture technique with the best ultrastructural preservation in combination with the best embedding and contrasting technique for visualizing neuronal elements. Two induced neural stem cell lines derived from healthy control subjects underwent differentiation either adherent on glass coverslips, embedded in a droplet of highly concentrated Matrigel, or as a compact neurosphere. Afterward, they were fixed using a combination of glutaraldehyde (GA) and paraformaldehyde (PFA) followed by three approaches (standard stain, Ruthenium red stain, high contrast en-bloc stain) using different combinations of membrane enhancing and contrasting steps before ultrathin sectioning and imaging by TEM. The compact free-floating neurospheres exhibited the best ultrastructural preservation. High-contrast en-bloc stain offered particularly sharp staining of membrane structures and the highest quality visualization of neuronal structures. In conclusion, compact neurospheres growing under free-floating conditions in combination with a high contrast en-bloc staining protocol, offer the optimal preservation and contrast with a particular focus on visualizing membrane structures as required for analyzing synaptic structures.
KW  - transmission electron microscopy
KW  - human neurons
KW  - induced neural stem cells
KW  - synapse
KW  - synaptic vesicles
KW  - high contrast
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-236053
SN  - 1422-0067
VL  - 21
IS  - 5
ER  - 
TY  - JOUR
A1  - Steigerwald, Frank
A1  - Müller, Lorenz
A1  - Johannes, Silvia
A1  - Matthies, Cordula
A1  - Volkmann, Jens
T1  - Directional deep brain stimulation of the subthalamic nucleus: a pilot study using a novel neurostimulation device
JF  - Movement Disorders
N2  - Introduction
A novel neurostimulation system allows steering current in horizontal directions by combining segmented leads and multiple independent current control. The aim of this study was to evaluate directional DBS effects on parkinsonian motor features and adverse effects of subthalamic neurostimulation. 

Methods
Seven PD patients implanted with the novel directional DBS system for bilateral subthalamic DBS underwent an extended monopolar review session during the first postoperative week, in which current thresholds were determined for rigidity control and stimulation-induced adverse effects using either directional or ring-mode settings.

Results
Effect or adverse effect thresholds were modified by directional settings for each of the 14 STN leads. Magnitude of change varied markedly between leads, as did orientation of optimal horizontal current steering. 

Conclusion
Directional current steering through chronically implanted segmented electrodes is feasible, alters adverse effect and efficacy thresholds in a highly individual manner, and expands the therapeutic window in a monopolar review as compared to ring-mode DBS.
KW  - deep brain stimulation
KW  - Parkinson's disease
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187683
VL  - 31
IS  - 8
ER  -