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Perhaps these investigators actually had membranes attached to their
electrode (in patch-clamp this is certainly true) while the rest of the
cell disintigrated.  I know you can do some sorts of recordings on
excised membrane patches- whether they look like action potentials, I
don't know.  Anyhow, I'd probably use an ion indicator to indirectly
measure the resting potentials of the cells.  For instance, resting
calcium levels tend to be higher in cells with a less negative resting
potential.  Which one to use is the question and you'd have to do a lot
of calibrations probably.
Sarah 

-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On
Behalf Of Philip Oshel
Sent: Thursday, November 09, 2006 7:58 AM
To: [log in to unmask]
Subject: Re: Voltage sensitive dye for the membrane potential...

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Yeah, sounds wierd -- but what what I meant was the cells were dead 
and they were getting action potentials, and the experiments were 
continued long enough for the membranes to be lost also, not that the 
action potentials were coming from dead cells with no membranes. I 
wan't the only one who noticed this.
Phil

>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Hmm action potentials without membranes? I had better revise my 
>teaching on the biophysics of  cells!
>
>LOL
>
>Cheers
>
>
>Philip Oshel wrote:
>
>>  Search the CONFOCAL archive at
>>  http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>>
>>  I'm not so sure about that. Action potentials can be gotten from 
>>dead neurons. I worked in a lab once doing EM for a bunch of 
>>neurophysiologists, and they routinely got action potentials not 
>>only from dead brain slices, but also slilces where the neurons had 
>>been dead long enough to lose their membranes. (Needless to say, 
>>they never liked being told this.)
>>
>>  But, I think there's a typo here. Tino refers to "slice 
>>preparation", which is a tissue sample thick enough to contain 
>>living, intact cells, not to "slide preparation".
>>
>>  Phil
>>
>>
>>>  Yes, but I don't quite understand what Tino means by
>>>  slide preparations.  You'll only get a measure of
>>>  membrane potential is the cells are intact and alive.
>>>
>>>                      Guy
>>>
>>>  moreno wrote:
>>>
>>>>   yes,
>>>>   DI8-ANNEPS for example.
>>>>   Tino Jaeger wrote:
>>>>
>>>>>   Hi,
>>>>>
>>>>>   is there any fluorescence dye, which can can be used to code for
the
>>>>>   membrane potential of cells (e.g. loading of the cells like 
>>>>>with FURA-AM,
>>>>>   and the then fluorescence intensity of the dye shows up the
different
>>>>>   voltage (membrane potential) of cells in a slice preparation)?
>>>>>
>>>>>   Thanks for your help.
>>>>>   Tino
>>>>>
>>>>
>>>
>>>  -- ______________________________________________
>>>  Associate Professor Guy Cox, MA, DPhil(Oxon)
>>>  Electron Microscope Unit, Madsen Building F09,
>>>  University of Sydney, NSW 2006
>>>  ______________________________________________
>>>  Phone +61 2 9351 3176     Fax +61 2 9351 7682
>>>  Mobile 0413 281 861
>>>  ______________________________________________
>>>  http://www.guycox.net
>>
>>

-- 
Philip Oshel
Microscopy Facility Supervisor
Biology Department
Central Michigan University
024C Brooks Hall
Mt. Pleasant, MI 48859
voice: (989) 774-3576
dept. fax: (989) 774-3462