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Electrophysiological Recordings on a Sounding Rocket: Report of a First Attempt Using Xenopus laevis Oocytes

Simon L. Wuest
Simon L. Wuest
, 
Tobias Plüss
Tobias Plüss
, 
Christoph Hardegger
Christoph Hardegger
, 
Mario Felder
Mario Felder
, 
Aaron Kunz
Aaron Kunz
, 
Benno Fleischli
Benno Fleischli
, 
Carlos Komotar
Carlos Komotar
, 
Lukas Rüdlinger
Lukas Rüdlinger
, 
Andreas Albisser
Andreas Albisser
, 
Thomas Gisler
Thomas Gisler
, 
Daniela A. Frauchiger
Daniela A. Frauchiger
 and 
Marcel Egli
Marcel Egli
   | Jul 21, 2020
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Article Category: Research Article
Published Online: Jul 21, 2020
Page range: 43 - 56
DOI: https://doi.org/10.2478/gsr-2017-0010
Keywords
© 2017 Simon L. Wuest et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Schematic of the recording principle. An oocyte was placed in the cavity of a silicone chip (light green) and pressed against a small aperture at the lower end, which electrically isolated a patch of the cell membrane. The silicone chip was stabilized with a glass slide (dark green). With the help of four electrodes, a defined voltage was applied across the membrane patch and the corresponding current was measured. The medium in the lower compartment was exchangeable to allow application of different media or drugs.
Schematic of the recording principle. An oocyte was placed in the cavity of a silicone chip (light green) and pressed against a small aperture at the lower end, which electrically isolated a patch of the cell membrane. The silicone chip was stabilized with a glass slide (dark green). With the help of four electrodes, a defined voltage was applied across the membrane patch and the corresponding current was measured. The medium in the lower compartment was exchangeable to allow application of different media or drugs.

Figure 2

Schematic of the air and liquid system. Air pressure from the reservoir was reduced and regulated to the appropriate level by three pressure controllers: perfusion, top, and waste pressure. The perfusion pressure was used for the flow of the medium through the recording chambers, the top pressure ensured proper placement of the oocytes, and the third pressure controller released the pressure from the waste container as medium was transferred. Fresh medium was distributed from medium container to the two late access modules. In the late access module, the medium lines were split further, leading to valves that controlled the flow of the medium through the chambers. The medium passed through capillaries before reaching the recording chambers, which ensured a constant flow (not shown in the illustration). After the recording chamber, the medium passed through a waste medium valve, which was closed during launch and in case of malfunction. Then, the waste medium was brought to an intermediate waste medium container before leaving the late access module (not shown in schematic). From there, the medium was finally collected in a waste medium bag.
Schematic of the air and liquid system. Air pressure from the reservoir was reduced and regulated to the appropriate level by three pressure controllers: perfusion, top, and waste pressure. The perfusion pressure was used for the flow of the medium through the recording chambers, the top pressure ensured proper placement of the oocytes, and the third pressure controller released the pressure from the waste container as medium was transferred. Fresh medium was distributed from medium container to the two late access modules. In the late access module, the medium lines were split further, leading to valves that controlled the flow of the medium through the chambers. The medium passed through capillaries before reaching the recording chambers, which ensured a constant flow (not shown in the illustration). After the recording chamber, the medium passed through a waste medium valve, which was closed during launch and in case of malfunction. Then, the waste medium was brought to an intermediate waste medium container before leaving the late access module (not shown in schematic). From there, the medium was finally collected in a waste medium bag.

Figure 3

Schematic illustrating the structure of the experiment. The structure organized the experiment across four decks. Two gas cartridges, pressure controllers, and containers for fresh and waste medium were mounted on the lowest deck. Two late access modules were placed on the two middle decks, and three recording chambers were placed in each. The board computer and associated electronics were mounted on the top deck.
Schematic illustrating the structure of the experiment. The structure organized the experiment across four decks. Two gas cartridges, pressure controllers, and containers for fresh and waste medium were mounted on the lowest deck. Two late access modules were placed on the two middle decks, and three recording chambers were placed in each. The board computer and associated electronics were mounted on the top deck.

Figure 4

Cross-section view of the recording chamber. The recording chamber accommodated one oocyte, allowing the medium in contact with the patch of the cell membrane to be exchanged, and providing the mechanical support for the electrodes and connecting tubes. The oocyte (black and white) was pressed in a cavity of a silicone chip (light blue), which had a tiny hole at the lower end. The chip was reinforced with a glass slide (gray), and the tiny hole was formed with a ruby bearing (red). The exchange of the medium in contact with the membrane patch was accomplished with a micro-fluidic chip (dark blue). A polymethyl methacrylate (PMMA) housing held the two silicone chips, the electrodes, and the tubing for the fluids in place.
Cross-section view of the recording chamber. The recording chamber accommodated one oocyte, allowing the medium in contact with the patch of the cell membrane to be exchanged, and providing the mechanical support for the electrodes and connecting tubes. The oocyte (black and white) was pressed in a cavity of a silicone chip (light blue), which had a tiny hole at the lower end. The chip was reinforced with a glass slide (gray), and the tiny hole was formed with a ruby bearing (red). The exchange of the medium in contact with the membrane patch was accomplished with a micro-fluidic chip (dark blue). A polymethyl methacrylate (PMMA) housing held the two silicone chips, the electrodes, and the tubing for the fluids in place.

Figure 5

Schematic of the intermediate waste medium container. To ensure a constant pressure at the recording chamber outlet, an intermediate waste medium container was mounted on the front side of the late access module. The waste lines from the recording chambers entered the upper part of this container. A further connection enabled fast pressure equilibration to the waste medium container (reference pressure). At the lower end, a tube was connected to the waste medium container, allowing the medium to drain.
Schematic of the intermediate waste medium container. To ensure a constant pressure at the recording chamber outlet, an intermediate waste medium container was mounted on the front side of the late access module. The waste lines from the recording chambers entered the upper part of this container. A further connection enabled fast pressure equilibration to the waste medium container (reference pressure). At the lower end, a tube was connected to the waste medium container, allowing the medium to drain.

Figure 6

Late access module insertion. To keep the oocytes as fresh as possible, they were inserted into the rocket shortly before launch. Two late access modules and the fresh medium container were inserted through a late access hatch. These three elements were prepared in the laboratory before launch and combined into a single unit with a removable handle; the handle was removed before the hatch was closed. The connection of the liquid tubes was made with quick dry connectors. The electrical connections were standard D-sub connectors, which automatically made electrical contact when the late access module was inserted. The left panel is a schematic of a computer model to show how the late access module was inserted into the rocket module. The right panel is an image of the late access shortly before launch.
Late access module insertion. To keep the oocytes as fresh as possible, they were inserted into the rocket shortly before launch. Two late access modules and the fresh medium container were inserted through a late access hatch. These three elements were prepared in the laboratory before launch and combined into a single unit with a removable handle; the handle was removed before the hatch was closed. The connection of the liquid tubes was made with quick dry connectors. The electrical connections were standard D-sub connectors, which automatically made electrical contact when the late access module was inserted. The left panel is a schematic of a computer model to show how the late access module was inserted into the rocket module. The right panel is an image of the late access shortly before launch.

Figure 7

Schematic illustration of the electronics. The electronics were distributed across four PCBs that were interconnected by a CAN bus: one main board for the board computer, two measurement units, and one power supply unit. The board computer was the controlling unit of the experiment and was responsible for correctly executing the experiment protocol, saving the measured data (on two nonvolatile storage devices), controlling the pressure regulators, recording the acceleration, and communicating with the rocket's service module. The measurement units controlled the voltages applied to the oocytes and measured the effective applied voltage and the corresponding current. Further, they switched the valves and recorded the temperature (temp.) in the recording chambers. While still on the ground, they also controlled heating foils under the recording chambers should the chambers become too cold. The rocket's service module provided the experiments with power, inflight signals, and an RS422 serial communication interface. The 28 V power supply from the service module was converted by the power supply unit to the various voltage levels required. Three signals were submitted during the countdown and flight to synchronize the board computer with the major flight events. The serial communication interface allowed for data downlink during the flight and commanding via uplink while the rocket was still on the ground.
Schematic illustration of the electronics. The electronics were distributed across four PCBs that were interconnected by a CAN bus: one main board for the board computer, two measurement units, and one power supply unit. The board computer was the controlling unit of the experiment and was responsible for correctly executing the experiment protocol, saving the measured data (on two nonvolatile storage devices), controlling the pressure regulators, recording the acceleration, and communicating with the rocket's service module. The measurement units controlled the voltages applied to the oocytes and measured the effective applied voltage and the corresponding current. Further, they switched the valves and recorded the temperature (temp.) in the recording chambers. While still on the ground, they also controlled heating foils under the recording chambers should the chambers become too cold. The rocket's service module provided the experiments with power, inflight signals, and an RS422 serial communication interface. The 28 V power supply from the service module was converted by the power supply unit to the various voltage levels required. Three signals were submitted during the countdown and flight to synchronize the board computer with the major flight events. The serial communication interface allowed for data downlink during the flight and commanding via uplink while the rocket was still on the ground.

Figure 8

Graph depicting the current signal after medium switches. The oocyte membrane patch was normally perfused with 100Na. When medium was switched from 100Na to 100Ch and back, a small and unspecific reaction was provoked from native oocytes, likely since 100Ch possesses very few cations. The graph indicates the current signal after switching from 100Na to 100Ch (blue line), and from 100Ch to 100Na (red line). The signals were shifted such that 0 seconds indicates the switching events. The holding voltage across the oocyte was kept at 0 mV.
Graph depicting the current signal after medium switches. The oocyte membrane patch was normally perfused with 100Na. When medium was switched from 100Na to 100Ch and back, a small and unspecific reaction was provoked from native oocytes, likely since 100Ch possesses very few cations. The graph indicates the current signal after switching from 100Na to 100Ch (blue line), and from 100Ch to 100Na (red line). The signals were shifted such that 0 seconds indicates the switching events. The holding voltage across the oocyte was kept at 0 mV.

Figure 9

The acceleration and altitude profiles recorded by the REXUS service module. The top graph shows the acceleration profile with the major flight events indicated by arrows. The bottom graph shows the altitude profile. Because REXUS 20 was longer and heavier than previous REXUS rockets, the apogee was lower than usual. Data were provided by the Mobile Rocket Base (MORABA) from the German Aerospace Center (DLR).
The acceleration and altitude profiles recorded by the REXUS service module. The top graph shows the acceleration profile with the major flight events indicated by arrows. The bottom graph shows the altitude profile. Because REXUS 20 was longer and heavier than previous REXUS rockets, the apogee was lower than usual. Data were provided by the Mobile Rocket Base (MORABA) from the German Aerospace Center (DLR).

Figure 10

Representative reading of a recording chamber during launch (liftoff at 0 seconds). The board computer triggered a voltage jump at liftoff to assess whether the liftoff signal was received and to obtain a measurement of the seal resistance. A sharp drop in the applied voltage, accompanied by a sharp rise in the current signal, was observed a few seconds into the flight (arrow). Since the recording chambers all appeared empty as the rocket reached the microgravity phase, this event likely indicates the time point when the oocytes were ripped apart.
Representative reading of a recording chamber during launch (liftoff at 0 seconds). The board computer triggered a voltage jump at liftoff to assess whether the liftoff signal was received and to obtain a measurement of the seal resistance. A sharp drop in the applied voltage, accompanied by a sharp rise in the current signal, was observed a few seconds into the flight (arrow). Since the recording chambers all appeared empty as the rocket reached the microgravity phase, this event likely indicates the time point when the oocytes were ripped apart.
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