Jeff de Ropp
UCD NMR Facility
jsderopp@ucdavis.edu
Phone: 916-752-7677
FAX: 916-752-3516
NMR Facility URL http://www.nmr.ucdavis.edu
*************************************
>From cgregory@uiuc.eduThu Aug 10 08:23:42 1995
Date: Wed, 09 Aug 1995 17:38:35 -0500
From: Carl Gregory <cgregory@uiuc.edu>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Perfusion & Flooding
>We have several users in our lab who do experiments on various
>sorts of tissues that they nourish while in the magnet via an assortment of
>different perfusion equipment.
>Most of the time this works well but occasionally a leak will develop,
>flooding the probe. Generally the flood comes about through the liquid
>in the tube overflowing into the probe. No matter
>how much care is used eventually a probe will periodically get flooded.
>My question to the group is two-fold:
>1) Has anyone come up with perfusion setup for a NMR magnet that they
>have found to be COMPLETELY leak-proof?
>2) Failing that, has anyone heard of or used a sensor that could detect
>(for example) a too-high level of liquid in a NMR tube and set off some
>sort of alarm?
>
>Please send responses to me and I will post a summary if there is general
>interest.
Jeff -
The short answers first: No and No.
We also do this (superfusion) a lot. The only foolproof way to do it is to
have a completely sealed system (we have one such homebuilt probe, which
operates with a gravity feed, thus avoiding overpressure situations).
Most of our work is done with open NMR tubes (20mm). We put two teflon or
poly tubes down into the nmr tube - one to the bottom (fluid in) and one to
a point a few cm below the top. These are attached to the NMR tube cap
(provided also with an air hole) to hold them in while the tube is lowered
into the magnet. The outlet tube is attached to a "T", and both arms of the
"T" go to a 4-channel peristaltic pump. The inlet tube goes directly to the
pump. (The 4th channel is unused). This arrangement results in having 2x
the suction rate as the inlet rate, thus preventing overflows. The system
is easily monitored - as long as there is a continuous air-bubble train in
the outlet tube, everything is probably ok.
Nevertheless, this system does overflow (about once a year over the last 8
years) due to various reasons - a tube being yanked out, tissue plugging the
outlet tube orifice, or carelessness. So I'm interested in any neat
suggestions anyone else has!
I recently had our 20mm probe apart for other reasons, and noticed a few
dried droplets of saline inside, but no gross corrosion, as one might have
expected. Apparently the overflow mostly goes outside the probe (presumably
the VT air pressure keeps it from getting into the small space between the
NMR tube and insert).
Good luck.
Carl Gregory
Biomedical Magnetic Resonance Lab
University of Illinois College of Medicine
Urbana, IL
*********************************************
>From simonw@gene.comThu Aug 10 08:23:49 1995
Date: Wed, 9 Aug 1995 16:49:37 -0800
From: Simon Williams <simonw@gene.com>
Reply to: williams.simon@gene.com
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Perfusion & Flooding
I've done a lot of perfusions and had a few floods in my time, but think
good working practice rather than "leakproof" systems are required. The
Titanic was unsinkable, after all. If you want to be sure, it helps to
have two independent systems for removing the liquid from the probe,
each capable of coping with all the influent. Keep all pump tubing in
good order, and best of all make such users stay in the magnet room
throughout the experiment and keep an eye on it. Prove the viability of
systems used with long bench-tests; don't forget a sample - they
significantly increase resistance to flow in the tube or whatever.
You may have problems with liquid getting into the RT shim set as well
as the probe itself depending on the nature of the flood; if it starts
high up and creeps down the bore it typically goes round the probe into
the shims.
Happy flooding,
Simon Williams
****************************************
>From strain@mango.uoregon.eduThu Aug 10 08:24:25 1995
Date: Wed, 9 Aug 1995 17:54:18 -0700 (PDT)
From: Michael Strain <strain@mango.uoregon.edu>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Perfusion & Flooding
Jeff,
How about a skinny tube dipping into the upper part of the NMR vessel
that is hooked to some sort of (reliable) suction pump that is
constantly sucking away any liquid that reaches it?
I have absolutely no experience in this area except for a recent trip
to the dentist's office.
--Mike
-----------------------------------------------------------------------
Michael Strain strain@mango.uoregon.edu
Institute of Molecular Biology "Lunch et Veritas"
University of Oregon voice: 503-346-4036
Eugene, OR 97403 FAX: 503-346-4854
-----------------------------------------------------------------------
**************************************
>From g-sukenick@ski.mskcc.orgThu Aug 10 08:24:36 1995
Date: Thu, 10 Aug 1995 09:26:52 -0400
From: "George D. Sukenick" <g-sukenick@ski.mskcc.org>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Perfusion & Flooding
>We have several users in our lab who do experiments on various
>sorts of tissues that they nourish while in the magnet via an assortment of
>different perfusion equipment.
>2) Failing that, has anyone heard of or used a sensor that could detect
>(for example) a too-high level of liquid in a NMR tube and set off some
>sort of alarm?
If fluid is being injected into the probe, isn't there an exit tube to take
care of
outlet?? I would think that an NMR tube with screw cap and HPLC fittings might
work. If you are dealing with aqueous solution, a pair of Pt wires and a
conductivity
bridge (or even stick an op amp across and a buzzer) could detect high
level. There
are companies which make level detectors; you'd just have to adapt them so
that the
electronics are out of the magnet :-) Or maybe the experimental setup
isn't what I
picture in my mind.
I might be able to give more specific suggestions if you give me more info,
such as tube
size, general set up of experiment, etc.
good luck,
-george
g-sukenick@ski.mskcc.org
******************************************************
>From jbv@iris1.sb.fsu.eduThu Aug 10 08:24:43 1995
Date: Thu, 10 Aug 95 09:26:30 -0400
From: Joseph <jbv@iris1.sb.fsu.edu>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: Re: Perfusion & Flooding
We have some biologists who do these exps frequently. Contact:
Ross Ellington elling@bio.fsu.edu
Tim Moerland moerland@bio.fsu.edu
Steve Kinsey kinsey@magnet.fsu.edu
Chris Combs combs@magnet.fsu.edu
Dr. Joseph Vaughn, Manager NMR Facility
Chemistry Department
Florida State University
Tallahassee, FL 32306
Phone 904-644-3334
-9636
Fax 904-644-8281
*********************************
>From numare@cnj.digex.netThu Aug 10 08:25:10 1995
Date: Thu, 10 Aug 95 09:29:25 PDT
From: Lawrence Byrnes <numare@cnj.digex.net>
To: Jeffrey Deropp <jsderopp@ucdavis.edu>
Subject: RE: Perfusion & Flooding
10 August 1995, Thursday, 0930
Dear Jeff
I built a device for monitoring an ongoing chemical reaction. It made use of a peristaltic
pumping system. A very fine capillary was introduced into the spinning nmr tube. It never
leaked. If you would like more information I'll have to go back to my graduate school records.
Best Regards,
Lawrence Byrnes
******************************************
>From bray@indyvax.iupui.eduThu Aug 10 13:28:13 1995
Date: Thu, 10 Aug 1995 11:09:33 +0000
From: "Bruce D. Ray" <bray@indyvax.iupui.edu>
To: jsderopp@ucdavis.edu
Subject: Re: Perfusion & Flooding
>We have several users in our lab who do experiments on various
>sorts of tissues that they nourish while in the magnet via an assortment of
>different perfusion equipment.
>Most of the time this works well but occasionally a leak will develop,
>flooding the probe. Generally the flood comes about through the liquid
>in the tube overflowing into the probe. No matter
>how much care is used eventually a probe will periodically get flooded.
>My question to the group is two-fold:
>1) Has anyone come up with perfusion setup for a NMR magnet that they
>have found to be COMPLETELY leak-proof?
Well, I've collaborated with the physiology department of IU School of
Medicine on some dog pulmonary artery perfusion experiments, and I
have never had a leak in my setup. This doesn't mean that I can prove
that the setup is completely leak-proof, but I think a three year track
record (fall 1990 - fall 1993) of weekly experiments with no leaks is
suggestive. Before explaining the setup, please note that everything
I describe was designed based on things I saw in the late 70's and
early 80's at the Purdue Biochemical Magnetic Resonance Laboratory,
and I believe that some or all of Professor Markley, Dr. Milo Westler,
and Dr. Bob Santini deserve credit for the ideas which led to this design.
{I'd give credit more accurately, but I just don't know who all was
responsible for what I only saw a couple of times.}
Our setup is gravity feed with active pump-out using a four channel
peristaltic pump running at a higher rate than the gravity feed in-flow
rate. Obviously, we do not recirculate perfusate, and oxygenation,
perfusate temperature regulation, etc. must take place at the top of the
gravity feed system. In practice, our system starts with a resevoir
dripping at a rate controlled by an externally applied plastic clamp
into a glass oxygenation and temperature regulation apparatus all
mounted on a wooden platform on the top of a non-magnetic platform
ladder. From this, the perfusate is fed into Norton phar-med (tm)
tubing and the rate of flow is regulated by another plastic clamp. This,
then, goes to the cap of the NMR tube where it is fed into polyethylene
tubing passed through the cap of the NMR tube. This perfusate in
tubing goes to the bottom of the NMR tube. From the top of the desired
liquid level in the NMR tube we run two larger diameter pieces of
polyethylene tubing passed through the cap of the NMR tube, and
connected outside the NMR tube to tygon tubing which runs up the
bore of the magnet. The tygon tubing runs to two channels of the
four channel peristaltic pump to actively pump out the perfusate.
About 1/2 inch higher in the NMR tube, we place a second set of two
polyethylene tubing pieces connected to the peristaltic pump in a
similar fashion to provide a backup. The peristaltic pump is set at
high speed to give a pumping rate on each channel greater than the
gravity feed rate {we tried to have it be twice as much}. The entire
setup should be constantly monitored since power failure can still
cause flooding of the probe {presumably, a shutoff solenoid on the
gravity feed line could prevent this}. Of course, flow rates for gravity
feed must have been setup with dummy samples held outside the
magnet at the level the real sample will have when in the probe
A few words about lowering the sample into the probe with this
assembly are in order. Modern NMR spectrometers have the nasty
habit of causing the tube to turn slightly while lowering the tube.
Therefore, we found it necessary to manually disconnect the spinner
gas line from the upper barrel. Furthermore, kinks in the tubing
can cause severe problems. Therefore, two people are required to
lower the sample into the probe. One person handles the insert
controls at the console. The other keeps the tubing straight and
allows the lowering of the tube to proceed by feeding tubing as the
NMR tube lowers.
>2) Failing that, has anyone heard of or used a sensor that could detect
>(for example) a too-high level of liquid in a NMR tube and set off some
>sort of alarm?
I2R {Instruments for Research and Industry, Inc., P.O. Box 159C,
Cheltenham, PA 19012} sells a liquid level monitor which uses a
stick-on infrared sensor, but I don't believe that the sensor can be used
with an NMR probe and spinner. It might be possible to modify a
spinner to incorporate the sensor, however.
-- Bruce D. Ray bray@indyvax.iupui.edu Operations Director NMR Center IUPUI Physics Dept. 402 N. Blackford St. Indianapolis, IN 46202-3273voice: 317-274-6914 fax: 317-274-2393 ************************************************ >From jelicks@aecom.yu.eduThu Aug 10 13:28:52 1995 Date: Thu, 10 Aug 1995 14:45:31 -0400 From: "Dr. Linda Jelicks" <jelicks@aecom.yu.edu> To: Jeffrey Deropp <jsderopp@ucdavis.edu> Subject: Re: Perfusion & Flooding
We also do perfusion experiments and have in the past had problems with probe flooding. The experiments in 5 and 10 mm tubes seem to be most problematic for us. We did find that the company I2R had some alarm systems which would detect liquid and could possibly be used to then shut off power to the inflow pump and prevent flooding. We did not purchase any of these devices however a student in the lab designed his apparatus to have inflow and outflow tubing as well as a second outflow line which was raised above the desired liquid level. It was attached to a trap and the house vacuum line. This setup worked very well for his experiments which were successfully completed without further flooding incidents.
Good luck with designing a completely leak proof system. I would be interested in your compilation of responses.
Regards, Linda Jelicks Linda A. Jelicks Assistant Professor Department of Physiology and Biophysics Albert Einstein College of Medicine 1300 Morris Park Avenue Bronx, New York 10461 718-430-2722 (phone) 718-430-8819 (fax) ********************************************* >From newage!joef@uucp-1.csn.netMon Aug 14 08:55:32 1995 Date: Sat, 12 Aug 95 15:48:41 MDT From: Joe Ford <newage!joef@uucp-1.csn.net> To: jsderopp@ucdavis.edu Subject: Perfusion problems
Just a suggestion, you may want to check with Doug Lewendowski (I think I spelled that right) at Harvard probably in the Medical School - Cardiology.
Good luck with your plumbing.
Joseph Ford Otsuka Electronics joef@otsuka.com *************************************************** >From newage!diverdi@uucp-1.csn.netMon Aug 14 08:55:55 1995 Date: Sun, 13 Aug 95 19:47:46 MDT From: Joseph DiVerdi <newage!diverdi@uucp-1.csn.net> To: jsderopp@ucdavis.edu Subject: Re: Perfusion & Flooding
While I was a post doc at (then) Bell Labs I saw a very nice perfusion apparatus that oas open at the top of the organ chamber. The chamber was drained by a piece of tubing connected to an aspirator so that the excess perfusate was conveniently removed. Additionally, the tubing inlet was placed above the organ so that the organ was bathed externally and the bulk suseptability was somewhat matched. Good Luck.
Regards, JAD 13 August 1995 diverdi@otsuka.com