Please select a topic from the following that best relates to your question.
General
Device and Hardware
Software
Experimental - Noise
Experimental- Measurement
Experimental- Acute slices
Experimental - Culture
Applications
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General
I
am not an electrophysiologist. Can I use the MED 64 system to
record physiological data from brain slices?
Yes. If you can
prepare good slices, you can record physiological data with
the MED64 system. With the MED64 system, there is no need to
manipulate glass electrodes for recording or stimulation.
Because of its low-impedance electrodes, noise level is low
and signals are acquired easily even from acute slices. The
MED64 system makes electrophysiology accessible to researchers
from other disciplines.
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Device and Hardware - General
How does the MED probe detect electric potential?
The equivalent circuit of planar microelectrode was described by D. A. Robinson, "The electrical properties of metal microelectrodes," Proc. IEEE, vol.56, pp.1065-71, June 1968, and G. Gross, "Simultaneous Single Unit Recording in vitro with a Photoetched Laser Deinsulated Gold Multimicroelectrode Surface," IEEE Transactions on Biomedical Engineering, vol. BME-26, No.5, May 1979.
Is the field potential recorded with the MED System different from the one recorded with conventional glass electrode?
No. Both are theoretically and technically the same.
How long is the AD conversion time lag between the channels?
Since the A/D board works at 20MHz (50 ns clock), if you sample at 20 kHz, the time lag is 1.55 uS.
Time lag = Floor (20MHz/(Nch * Fs)) * 50 [ns];
where Floor(Z) is the greatest integer less than or equal to Z
Nch is number of channels
Fs is sampling frequency
What
peripheral environment is needed for the MED64 system? Do I
need a Faraday cage?
The MED64 system does not require a special
environment such as a Faraday cage or vibration isolation
table. Because of its low-impedance electrodes, the noise
level of the MED64 system is very low without these items.
Please install your MED64 system on a stable table and away
from any power supplies. Please refer to the MED64 system
Handbook vol.1 Hardware .
What
type of microscope is suitable for the MED64
system?
An inverted
microscope is recommended because the electrodes under
the slice can be seen clearly. The best magnification to capture the electrodes is
20x (10x for eyepiece and 2x for objective lens). However, at the MED
probe of MED-P210#, MED-P515#, and MED-P530#, all 64 electrodes can be captured with
up to 5x objective lenses.
Is
there any way to record from more than 1
sample?
The MED64 "Channel Divider" will allow you to
record from 4 slices and cultures. Please refer to the
brochure MED64 Channel divider.
Device and Hardware - MED
probe
How
many types of probes are available?
There are 18 types of probes available
currently. Please refer to the Probe specification
sheet
.
How
to coat the MED probe prior to use?
The surface of the
MED probe is relatively hydrophobic. Therefore, treatment with
poleythylenimine ( PEI
) is necessary for tissue adhesion.
Please refer to the PEI methods
for
the process.
How
can I store the used MED probe?
Fill a beaker with distilled water and put the
probe into it. Place the beaker in the refrigerator. Please
don’t leave it over a month.
Is
it okay to coat the probe more than once if the slice is not
adhering to the probe?
Yes,
it is okay to coat the probe more than once. However, after
repeated exposure to brain tissue and ACSF, the probe will
become more hydrophilic.
How
to clean the MED probe after use?
For acute slice
thoroughly rinse the probe under DI water (remember to keep
the electrodes moist at all times, especially over night). If
it is difficult to remove the slice due to adhision, please
try to remove the tissue and clean the probe using EDTA-Collagenase
probe reuse cleaning method.
For
slice culture please refer to EDTA-Collagenase
probe reuse cleaning method. Make sure not to
touch the fragile electrodes during cleaning, or while
removing a slice.
When
do I know if a probe is no longer usable?
One
indication that the probe may no longer be usable is erratic
noise coming from several electrodes. Be sure not to confuse
this with a bad connector/probe connection. The difference is
the presence of noise in an entire quadrant as opposed to
individual electrodes. Cleaning the connector contacts should
get rid of this problem.
Probe usage depends on proper care and
handling. Be sure never to touch the electrodes with a brush
or any other object. With proper care, a probe should last at
least 10 times and up to 30 times of usage. Please refer to Probe
reuse .
May
I autoclave MED probes?
No. Autoclave may damage the electrodes.
Please use ethanol (70%) and UV. Please refer to Collagen Gel Method
for a detailed
process.
Device and Hardware-MED Connector
Solution
has spilled over the MED-C03. What should I
do?
The
overflow of the solution will cause the contact pins to rust.
Please be extremely careful not to overflow the solution. Once
the solution is overflowed over the contact pins of the MED
connector, immediately wipe the pins with a clean cloth soaked
with distilled water gently so that salt materials will come
out. After that, dry it for a while (Don’t use alcohol, which
might remove the lubricant which is necessary for the movement
of pins.)
If
pins are stacked and unmoving, the connector needs to be
repaired. Contact our local distributor or support@med64.com.
It
seems that the connections of the pins are not good. How can I
improve them?
Wipe the pins while pushing them several
times with a lint-free cloth (E.g., lens cloth for glasses).
If it does not improve, your connector needs to be repaired.
Contact our local distributor in your region or support@med64.com
.
Some
pins are stacked and not moving. What should I
do?
The connector needs to be repaired.
Please contact your local distributor or
support@med64.com .
Device and
Hardware-PC
I
would like to reinstall my MED64 PC. How can I do
that?
You
need to reinstall National Instruments boards, National
Instruments drivers, and MED software. Please refer to page
43, “Reinstallation of MED64 computer” in the MED64
System Hand Book Vol.1
.
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Software
How
can I do LTP experiments with Mobius?
Please refer to
the Mobius Quick start
guide
.
Can
I do LTD experiments?
LTD experiments can be done with Mobius. They
cannot be done with Performer.
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Experimental - Noise
What
should the noise level be, and what are some of the best ways
to minimize noise?
The
noise level of the MED64 system is very low because of its
low-impedance electrodes (7-10 k ohm at 1 kHz typically.)
Noise levels differ from setup to setup, but the level usually
should be several micro volts at the time scale of 20
ms/division. The main ground should be simple by connecting
the MED amplifier and peripheral items such as perfusion cap,
peristaltic pump, and temperature controller in a single line.
Please don’t make a “ground loop”. Also, the level of the
solution must be high enough to cover all four reference
electrodes. Please refer to the MED64
System Handbook Vol.1
to help minimize noise.
Noise check
list
1)
Plug the amplifierand
peripheral items such as peristaltic pump and temperature
controller
into grounded
outlets
2)
Connect
the Connector
cable to
the grounding terminal on the back of the MED64 amplifier
with
the
green
grounding
wire
3)
Ground the platinum wire in the perfusion cap with the
Connector clip attached to the MED
connector.
4)
Are you using water instead of saline for the noise
test?
Are
all reference electrodes covered by
solution?
5) Try
a new probe.
6)
Uncoated
probe was stored dry - coat & sit overnight.
7)
Poor contact of MED connector- Wipe
the pins with a lint-free cloth.
8)
Perfusion noise-
1. Clean the inside of tubing, particularly dropper /
2. Wrap them with aluminum foil.
9)
Ground loop noise - only use one common
ground
10)
50/60Hz noise –
Check all grounding. Shield
and move cables away from the
MED Connector
11)
Very low frequency noise- 1. Check the stability of the table.
/ 2. Check the platinum wire fixed in the bottom of
chamber.
12)
Send
a data
file (spontaneous recording with saline only for a few
seconds) to
support@med64.com
Non-sinusoidal
wave noise is usually caused by magnetic fields. Make sure no pumps,
heaters, power supplies are placed near the RIGHT side of the
amplifier or MED connector cable.
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Experimental - Measurement
After
stimulation, the stimulus artifact is not visible on the
program. What is wrong?
If it is not visible at Conductor,
electrodes 1-32 and 33-64 are reversed. Switch the two NI
cables so that they are in the opposite position.
What
is the maximum stimulus current to be applied to the
electrodes?
Please refer to the
Operating
Instruction of MED probe.
Upon
stimulation, I see a large stimulation artifact. How can I
minimize the stimulus artifact?
The
stimulus artifact through MED64 system should be very small
because of its low-impedance electrodes. Please refer to the
page 37, “Stimulus artifact” in MED64
System Handbook, Vol.1
to minimize the stimulus artifact.
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Experimental - Acute slices
What
type of slicer should I use?
A
Vibratome type is strongly recommended because it can achieve
a flat surface of the slice, which is significant for
recording with multi electrode array.
When
I section the brain on the Vibratome it does not cut even
slices. And often times the brain will come off the base
plate. How can I avoid this?
Uneven
slices can occur when the temperature in the vibratome bath is
not ice-cold. Also, if the base of the brain is not
sufficiently dried, or not enough glue is used, the brain will
come off the base plate.
When
I section the brain on the Vibratome the lazer does not cut
the slice, but pushes it. How can I avoid
this?
Increase the frequency and slow the speed of the
Vibratome.
When
I put the slices into the oxygenated ACSF recovery chamber,
they look fine. But after an hour or so, they seem discolored
and less healthy. Why does this occur?
Slices
in the recovery chamber must be very well oxygenated. Also, if
the slices are too thick (>450 microns) the center of the
slice will become anoxic and cause discoloration.
How
to adhere the slice on the MED probe?
Use
the slice anchor. Please refer to MED64
Procedure.
After
putting the slice onto the MED probe, upon stimulation I can
not see any responses.
This is usually due to the slice not being fully
adhered on the electrodes particularly at the beginning of an
experiment. Make sure to use a slice anchor. Even with the
weight, it might take some time for a slice to adhere to the
electrodes after starting perfusion. You might need a larger
stimulus current to acquire evoked signals at the beginning of
an experiment.
After
putting the slice onto the probe, upon stimulation all I see
are large capacitance currents in many or all of the
electrodes. In addition, during recording, clear EPSP signals
continuously fade in and out. What is the cause of this
inconsistency?
This
is usually due to the slice not being fully adhered to the
probe. Using a weight should get rid of this
problem.
Once
the slice is on the probe, I've noticed that over time the
surface of the slice gets waxy. How can I avoid this?
Waxy
looking slices are caused by the airflow entering the probe.
Either too little or too much oxygen will cause this. Also, if
the level of ACSF within the probe is too low, the slice will
get dried out.
I can get good EPSPs immediately
after putting the slice onto the probe, but later, the
response goes away. How can I maintain a steady baseline?
The
major factors involved in maintaining a steady baseline are
controlling stable temperatures (incubator, baths, ACSF,
humidified oxygen), correct airflow, and a stable ACSF level
within the probe.
After
preparing the ACSF, I've noticed that the solution is
sometimes cloudy. Why does this occur?
ACSF
can become cloudy when it is left at a standstill without
oxygen for a prolonged period of time (greater than 30 min).
Therefore, the solution must be made fairly rapidly, and
exposed to oxygen, especially after adding the
MgSO4, NaHCO3, and CaCl2.
I have noticed that the temperature inside the probe
chamber changes frequently. How can I stabilize
this?
The best solution is to place the MED
connector and probe into incubator as seen in the picture on
page 35 of the MED64 system
Handbook Vol.1. If an incubator can not be used, warming the
solution and water humidifying air in the flask will be
helpful to keep the temperature.
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Experimental - Culture
How
long can I record neuronal activity using the MED
System?
You can record
from cultured neuron for months (see Shirakawa
et al., Honma
et al ., and Funabashi
et al ) and from acute slice for several hours
(see Oka et al., )
Neurons
grew on the reference electrodes, and I could not measure a
response.
A MED probe with a silicon ring glued around the
electrodes is available. Please contact support@med64.com.
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Applications
Can
I use the MED64 system for acute
slices?
Yes.
The low- impedance electrodes enable you to record good
signals easily even from acute slices.
Can I record activities from neurons cultured on
the MED probe?
Yes. This is actually the most intensively studied application of the MED System. Please refer to Shirakawa et al. , Honma et al ., and Funabashi et al .
Can I combine the MED64 system with patch clamp?
Yes. You may want to use MED probe with 5 mm chamber depth for easier approach of patch electrode from the top.
Can I combine the MED64 system with optical imaging?
Yes. Please refer to K. Kilborn et al, Society for Neuroscience abstracts 469.8 (2000)
Can I record myocardial cell activity with the MED64 System?
Yes. You can detect activity of any excitatory cells.
Can I record vermiculation movement of the intestines?
Because vermiculation is the process of wave-like muscle contractions, you can record it with the MED System. However, you may encounter noises from its physical movement.
Can I use the MED64 system with in vivo preparation?
No. MED64 System is designed for in-vitro preparation.
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