Cardiac pacing using transmural multi-LED probes in channelrhodopsin-expressing mouse hearts.

Optogenetics enables cell-type specific monitoring and actuation via light-activated proteins. In cardiac research, expressing light-activated depolarising ion channels in cardiomyocytes allows optical pacing and defibrillation. Previous studies largely relied on epicardial illumination. Light penetration through the myocardium is however problematic when moving to larger animals and humans. To overcome this limitation, we assessed the utility of an implantable multi light-emitting diode (LED) optical probe (IMLOP) for intramural pacing of mouse hearts expressing cardiac-specific channelrhodopsin-2 (ChR2). Here we demonstrated that IMLOP insertion needs approximately 20 mN of force, limiting possible damage from excessive loads applied during implantation. Histological sections confirmed the confined nature of tissue damage during acute use. The temperature change of the surrounding tissue was below 1 K during LED operation, rendering the probe safe for use in situ. This was confirmed in control experiments where no effect on cardiac action potential conduction was observed even when using stimulation parameters twenty-fold greater than required for pacing. In situ experiments on ChR2-expressing mouse hearts demonstrated that optical stimulation is possible with light intensities as low as 700 µW/mm2; although stable pacing requires higher intensities. When pacing with a single LED, rheobase and chronaxie values were 13.3 mW/mm2 ± 0.9 mW/mm2 and 3 ms ± 0.6 ms, respectively. When doubling the stimulated volume the rheobase decreased significantly (6.5 mW/mm2 ± 0.9 mW/mm2). We have demonstrated IMLOP-based intramural optical pacing of the heart. Probes cause locally constrained tissue damage in the acute setting and require low light intensities for pacing. Further development is necessary to assess effects of chronic implantation.

Versatile, modular 3D microelectrode arrays for neuronal ensemble recordings: from design to fabrication, assembly, and functional validation in non-human primates.

OBJECTIVE: Application-specific designs of electrode arrays offer an improved effectiveness for providing access to targeted brain regions in neuroscientific research and brain machine interfaces. The simultaneous and stable recording of neuronal ensembles is the main goal in the design of advanced neural interfaces. Here, we describe the development and assembly of highly customizable 3D microelectrode arrays and demonstrate their recording performance in chronic applications in non-human primates. APPROACH: System assembly relies on a microfabricated stacking component that is combined with Michigan-style silicon-based electrode arrays interfacing highly flexible polyimide cables. Based on the novel stacking component, the lead time for implementing prototypes with altered electrode pitches is minimal. Once the fabrication and assembly accuracy of the stacked probes have been characterized, their recording performance is assessed during in vivo chronic experiments in awake rhesus macaques (Macaca mulatta) trained to execute reaching-grasping motor tasks. MAIN RESULTS: Using a single set of fabrication tools, we implemented three variants of the stacking component for electrode distances of 250, 300 and 350 µm in the stacking direction. We assembled neural probes with up to 96 channels and an electrode density of 98 electrodes mm-2. Furthermore, we demonstrate that the shank alignment is accurate to a few µm at an angular alignment better than 1°. Three 64-channel probes were chronically implanted in two monkeys providing single-unit activity on more than 60% of all channels and excellent recording stability. Histological tissue sections, obtained 52 d after implantation from one of the monkeys, showed minimal tissue damage, in accordance with the high quality and stability of the recorded neural activity. SIGNIFICANCE: The versatility of our fabrication and assembly approach should significantly support the development of ideal interface geometries for a broad spectrum of applications. With the demonstrated performance, these probes are suitable for both semi-chronic and chronic applications.

Modular assembly concept for 3D neural probe prototypes offering high freedom of design and alignment precision.

The new assembly technology developed in this research provides a means to extend planar intracortical neural probes with one-dimensional (1D) and two-dimensional (2D) electrode arrangements into complex three-dimensional (3D) neural probes. The approach is based on novel silicon stacking modules realized using microsystems technologies. With these microcomponents, 3D probes can be assembled flexibly and tailored to the demands of neuroscientific experiments. The manufacturing process of the stacking modules provides the possibility to adjust the electrode spacing in the stacking direction with micrometer precision. The assembly method is demonstrated with 32-channel systems comprising 7-mm-long and 50-µm-thin neural probes. The angular alignment between the neural probes and their stacking modules after assembly as well as the vertical electrode pitch were determined to be about 1° and 353±15 µm, respectively.

Designing a study to evaluate the effect of apheresis in patients with elevated lipoprotein(a).

Lipoprotein(a) (Lp(a)) is a risk factor for premature coronary artery disease. Lp(a) levels can neither be influenced sufficiently by standard hypolipemic diet nor by drug therapy. Currently, lipid apheresis is the only option to effectively lower Lp(a) levels in patients with elevated Lp(a) and progressive CVD. The lipid-clinic at the Charité University hospital Berlin and other German apheresis centres have longstanding positive experience with this therapeutic regimen. Lately, in Germany lipid apheresis was accepted as the treatment of choice for patients with elevated Lp(a) levels > 60 mg/dl and progressive CVD. At the same time, care providers were obliged to conduct a controlled trial to prove the efficacy of lipid apheresis for this indication. Therefore, we designed a prospective, randomized, controlled trial to prove the hypothesis that lipid apheresis decreases vascular events.

[Perthes' disease, caused by initial sybovitis? (author's transl)]. / Morbus Perthes, Folge einer Synovitis?

An important factor in Perthes' disease is the primary affection of the nutritient vessels, though the etiology is unknown. The observation of four cases of painful hip disease with clinical symptoms of coxitis, but roentgenological and biopsy proofed evidence of aseptic necrosis of the epiphysis of the hip, gives reason to postulate the concept of initial synovitis as one of the possible causes of Perthes' disease. This concept is linked to Perthes-like pathology in cases of mediteranean fever with synovitis of the hip due to polyserositis. In the initial phase of the disease therapeutic consequences are antiinflammatory medication and early fluid aspiration from the joint to relief the intraarticular pressure.