The Medical College - Page 56
Three greenhouses were constructed to examine
dif-
ferent light cycles and their effects on the
growth of
several plants.
211.
Plant X requires 15 hours of light per day for
at
least three weeks to exhibit a red coloration in
its
leaves. It may exhibit this highly desired
feature
in:
A.
greenhouse 1.
B.
greenhouse 1 and 2.
C.
greenhouse 2 and 3.
D.
all of the above.
One hundred ml of blood was drawn from a
healthy
male donor. Following centrifugation (4°C)
and
removal of the "buffy coat" by aspiration,
hemoglobin
was extracted from the pelleted red blood cells.
The
extracted hemoglobin was then divided into
equal
aliquots and these were treated as
follows:
Aliquot 1: Analyzed on the day of extraction
by
polyacrylamide gel electrophoresis,
fol-
lowed by densitometer scanning of
the
stained gel
Aliquot 2: Stored for 30 days at room
temperature
Aliquot 3: Stored for 30 days at
4°C
Aliquot 4: Stored for 30 days as a 50%
solution
(V/V) in glycerol at –20°C
At the end of the 30-day storage period, each
of the
aliquots was analyzed in the same way as
aliquot 1.
The following densitometer tracings were
obtained:
212.
From these data it is clear that:
A.
none of the storage conditions were able
to
maintain hemoglobin in an
absolutely
unchanged state.
B.
hemoglobin peptides are strongly
affected
by heating.
C.
hemoglobin contains peroxidase
activity.
D.
hemoglobin coupled with oxygen has
a
longer self life than hemoglobin
coupled
with CO2.
Blood samples from 10 female rats were
withdrawn
at 5 PM on the day of proestrus, when LH levels
in the
blood should be high if ovulation were to occur
that
night. The blood was assayed by
double-antibody
radioimmunoassay for LH. An antibody specific
for
LH is allowed to bind with the LH in the
sample, then
is partially displaced by radiolabeled LH whose
bind-
ing to the limited amount of anti-LH is
inversely pro-
portional to the amount of unlabeled LH present
(see
standard curve). The antigen-antibody complex
is pre-
cipitated with an antibody to the anti-LH, and
the num-
ber of counts per minute bound in the
precipitate is
determined after the supernatant containing
the
unbound labeled LH has been poured off. The
blood
samples from 5 untreated rats (which ovulated)
had
cpm of 4000, 3000, 5000, 4000, and 3000,
whereas
those from 5 drug-treated animals had 5000,
13,000,
15,000, 3000, and 13,000.
213.
It can be concluded from this study
that:
A.
the untreated rats had very little LH in
their
blood compared to the treated
group.
B.
the drug does not block ovulation.
C.
the dose of the drug used in this
study
inhibits LH release in most of the
animals.
D.
ovulation occurred in three out of five
of
the treated rats.
.1
1
10
100
ng LH standard
15,000
10,000
5,000
CPM
bound
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