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Modified mice may hold key
to high blood pressure
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| Photo
by HSIMS These tiny telemeters shown on the palm of Dr. Bruce Van Vliet’s hand are surgically inserted into mice in order to transmit blood pressure readings 24 hours a day. |
Mice have become the new standard for researchers
studying the cardiovascular system.
“The mouse is now the Volkswagen of genetic change and has become
the workhorse – or workmouse of science,” said Dr. Bruce
Van Vliet, a researcher in basic medical sciences who is studying blood
pressure in mice.
Ten years ago, cardiovascular research was mainly on rats. But around
1990 molecular biologists began to make genetically modified mice. The
result was the ideal research tool – an animal with a very specific
change, perhaps just one deleted gene, could be produced. “It’s
a tremendous advantage to be able to study a single gene’s contribution
to something like high blood pressure, which affects one in five Canadians,”
said Dr. Van Vliet.
One of the problems in using mice is that they are very tiny, about
one-tenth the size of rats. “We didn’t have good ways to
measure their blood pressure and we also had to take into account that
although mice are like rats in a physiological and anatomical way, because
of their small mass and larger surface area they lose heat quickly and
must spend a lot of energy just to maintain body heat.”
Some researchers use a tail cuff to measure mouse blood pressure, but
it turns out that mice get extremely upset by the stress of this and
become hypertensive just from having the cuff on. Dr. Van Vliet has
found the most effective way to measure mouse blood pressure is with
tiny internally-inserted telemeters that emit a continuous radio signal.
A recent paper by Dr. Van Vliet, to be published in Physiology,
gives possibly the most detailed description ever done of blood pressure
in mice. “In this study we’ve paid attention to the effect
of locomotor activity on mouse blood pressure. It is very powerful in
changing their blood pressure – mice are either active or inactive.
Because they are small they have to eat frequently. Even during the
light period, when most nocturnal animals tend to be quiet, they have
six to eight bouts of activity gathering food. When they are active
their blood pressure goes up; when they are quiet it goes down.”
Dr. Van Vliet was recently awarded a $25,000 grant from Memorial’s
Medical Research Foundation (MRF) to study blood pressure in mice. “We’re
trying to promote and develop techniques to give confidence in the results
within a few percent. This still needs more understanding at the basic
level – with the help of the MRF funding, Alison Leonard is going
to work in my lab this summer and
start a master’s in the fall looking at the measurement of blood
pressure in mice.
Dr. Van Vliet said the MRF funding, although relatively small, allows
his lab to diversify. “We’ve been supported by the Canadian
Institutes of Health Research and we would like to interest NSERC (Natural
Sciences and Engineering Research Council) in supporting our projects.
But to submit an application we need our project to be fairly mature.
We’re already developing a reputation in this area and we’re
going to use the MRF funding to get the project focused specifically
on how to measure the blood pressure in a mouse – or to get more
technical about it, how to phenotype the blood pressure of a mouse.”
Dr. Van Vliet noted that other than the Faculty of Medicine’s
Medical Research Foundation and Dr. A. R. Cox awards, there are no provincial
sources of funding for basic medical research. “There is a tremendous
requirement for seed money in research. You need to find funding to
be able to follow leads and try new approaches. It takes a lot of funding
to come up with a project that will be supported federally.”
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