Creation
of
an
8-way
F1
cross
I.
Measuring
ear
pinna
length
a.
First
the
mice
are
weighed
using
a
top
loading
balance.
b.
Then
they
are
euthanized
by
exanguination.
c.
Ear
pinna
length
is
obtained
by
measuring
from
the
tip
to
the
base
of
the
pinna.
II.
Collecting
body
composition
scans
a. The
PIXImus
densitometer
apparatus
is
first
calibrated
with
a
"phantom
mouse"
according
to
manufacturer's
protocol.
b.
Then
each
mouse
is
placed
on
the
specimen
sticky
tray
(body
must
be
within
blue
line
on
tray)
under
the
PIXImus
beam
path.
The
tail
is
placed
alongside
the
body,
the
front
legs
are
extended
to
the
side,
and
the
neck
and
spine
are
gently
straightened.
c.
The
X-ray
process
to
obtain
a
single
full
scan
is
approximately
5
minutes;
data
can
be
manipulated
subsequently
to
obtain
specific
regions
of
interest.
d.
After
the
whole
body
(excluding
the
head)
is
scanned,
the
area
of
the
head
is
also
scanned.
e.
Trays
are
positioned
so
that
the
area
of
the
head
is
always
oriented
toward
the
left
from
the
investigator's
point
of
view,
and
the
mice
are
position
dorso-ventral
so
that
the
entire
body
and
tail
are
measured
in
the
scan.
For
more
details
see
PGA.
III.
Measuring
muscle
weight
a.
The
skin
and
subcutaneous
tissue
around
the
hind
limbs
is
removed
in
order
to
isolate
the
quadriceps
muscles.
b.
Using
a
small
(iris)
dissecting
scissors,
the
muscles
are
removed
from
their
origin
in
the
pelvic
bone
and
their
insertion
on
the
knee
joint
and
femoral
bone.
c.
Any
fat
depot
adjoining
the
muscles
is
removed
and
excluded
in
the
overall
weight.
Safety
For
safety,
gloves
must
be
worn
and
radiation
safety
guidelines
are
strictly
adhered
to,
such
that
technicians
must
be
6
feet
away
from
the
PIXImus
machine
during
scanning.
PIXImus
data
are
from
the
body
and
tail;
head
excluded.
BMD,
BMC,
total
tissue
mass,
and
%
fat
were
measured.
BMD
and
BMC
adjusted
for
body
mass
and
weights
of
lean
and
fat
portions
are
derived
and
are
available
in
the
data
set
for
analysis.
Notes
pertaining
to
the
data
set:PIXImus
scans
are
analyzed
using
the
PIXImus2
software
(version
1.46.007),
excluding
the
head
from
the
analysis.
Values
for
whole
body
(without
the
head),
both
femurs,
and
spine
were
obtained.
Left
femur
data
are
not
available
for
MPD
analysis
but
are
provided
in
the
project
data
set.
Test age:
7-8wks