Results (
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1.
Introduction
Interpol
recommends
the
use
of
muscle
tissue
only
in
cases
of
non-decomposed
remains.
What
defines
the
onset
of
decomposi
tion
is
not
specified,
although
agencies
typically
use
24
h
as
an
approximation
[1].
Studies
in
the
UK
in
the
summer
have
demonstrated
that
when
using
pigs
as
an
experimental
model,
DNA
up
to
400
bp
will
persist
for
up
to
3
weeks
[2].
Decomposition
of
tissues
is
a
process
that
depends
more
on
accumulated
temperature
rather
than
time.
Accumulated
degree
days
(ADD),
the
cumulative
total
of
daily
average
temperatures,
can
be
used
as
a
measure
to
estimate
post-mortem
interval
and
DNA
degradation
in
soft
tissues
[3].
As
it
is
known
that
DNA
degradation
is
influenced
by
temperature,
this
experiment
was
done
to
assess
DNA
persistence
in
soft
muscle
tissue
following
exposure
to
high
environmental
temperatures.
2.
Materials
and
methods
This
experiment
was
carried
out
during
June
2014
in
Thailand.
Whole
pig
carcasses
(Sus
scrofa)
and
separate
limbs
were
placed
in
direct
contact
with
the
ground.
Samples
were
collected
every
12
h
for
3
days.
Samples
collected
from
the
separate
limbs
were
collected
from
both
the
aerial
surface
(exposed
to
the
sun)
and
the
ground
surface.
After
collection,
samples
were
stored
in
ethanol
for
approximately
one
week
while
in
the
field,
and
frozen
prior
to
extraction
in
the
laboratory.
DNA
was
extracted
using
the
Qiagen
Blood
and
Tissue
Kit
and
evaluated
through
agarose
gel
electrophoresis
(AGE)
and
PCR.
A
species-specific
multiplex
that
amplified
amplicons
of
70
bp,
194
bp,
305
bp
and
384
bp
was
used;
the
PCR
were
analysed
using
an
ABI
3500.
3.
Results
and
discussion
The
average
ambient
temperatures
during
the
three
days
of
the
experiment
were
31?C
on
the
first
day,
33.5?C
on
the
second
day,
and
35.5?C
on
the
third
day.
The
average
internal
temperature
of
the
carcasses
was
of
33?C
(maximum
35?C),
31?C
(maximum
35?C)
and
35?C
(maximum
35.9?C)
respectively.
Degradation
was
visible
with
AGE,
with
its
characteristic
smears
that
appeared
after
16
ADD.
Samples
collected
after
36
h
were
not
detected
on
the
agarose
gel,
although
DNA
quantification
showed
the
presence
of
DNA.
The
exception
was
from
samples
that
*
Corresponding
author
at:
School
of
Forensic
&
Investigative
Sciences,
University
of
Central
Lancashire,
JB
Firth
Building,
Preston,
Lancashire
PR1
2HE,
UK.
Fax:
+44
1772
891990. E-mail address:
LVBaptista@uclan.ac.uk
(LV
. Baptista)
http://dx.doi.org/10.1016/j.fsigss.2015.09.086 1875-1768 / A 2015 เอลส์ Ireland Ltd. สงวน
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