The Medical College - Page 74
to either confirm or deny statement B,
however,
it is clear that Brown Norway rats
produced
antibody at both time periods and, therefore,
state-
ment A is supported by the data
presented.
206.
C.
From the experimental data, one can
con-
clude that prolactin and LH are both produced
by
the pituitary, and that the hypothalamus
stimulates
LH release, but inhibits prolactin release, and
that
ovarian hormones inhibit LH release, but not
pro-
lactin release. Lactogenic hormone or
luteotrophic
hormone (LTH) or prolactin is secreted by the
aci-
dophils (alpha cells) of the pituitary. This
hormone:
(1) promotes growth of the breast, which has
been
stimulated already by estrogen and
progesterone;
(2) promotes and maintains lactation; (3) helps
in
maintenance of the corpus luteum; and (4)
pro-
motes maternal instinct.
207.
C.
The experiment was performed to
determine
the effect of salinity concentrations on the
secretory
proteins of the urophysis. The data shows that
pro-
tein 2 was affected more (twice) by the
increasing
concentration of seawater than protein
1.
208.
D.
Careful analysis of the data shows that in
the
system under investigation, spleen cells and
mast
cells together are required for antibody
production,
that spleen cells are probably found in the
thymus
and that X-irradiation is an important tool
in
immunological work. Statement C, implying
that
spleen cells or mast cells are essential to the
anti-
body production against pollen is contradicted
by
the data because bone marrow and pollen and
thy-
mocytes and pollen show a response. Statement
D
is not supported or contradicted by the
experiment,
even though mast cells are known to produce
hista-
mine and their activity is controlled by
certain
nasal sprays limiting their effects after
exposure to
certain substances.
209.
C.
Beta cells of the pituitary produce
thyroid
stimulating hormone, which stimulates the
thy-
roid to produce its hormones
T3 (triiodothyronine)
and T4
(tetraiodothyronine or thyroxin).
Iodides
consumed in food and water are absorbed
and
carried to the iodide pool in the extracellular
fluid
via the circulatory system. Five events
are
involved in hormone production: (1)
trapping
iodide; (2) oxidation of iodide to organic
iodine;
(3) synthesis of hormone; (4) storage as the
thy-
roglobulin moiety; and (5) release of the
active
principle into the circulation. TSH greatly
influ-
ences the trapping mechanism; thiocyanates
block
trapping, whereas thiouracil blocks the
oxidation
and synthetic steps. The data show that Group
4
received thyroxine, which inhibited TSH
produc-
tion, whereas Group 2 was treated with
thicoy-
anate, which affected the iodine pump. Group
3
received propylthiouracil, an inhibitor of
iodine
oxidation; in Group 2 iodine is not taken up
and
no radioactivty can be measured.
210.
B.
The five-year total of wheat was 49; for
corn
it was 56. The ratio is thus
7/8.
211.
C.
Scanning of the graphs comparing the
num-
ber of daylight hours clearly shows that only
in
greenhouses 2 and 3 are there provided 15
hours
of light per day for several weeks, which is
neces-
sary for Plant X. If the question would have
been
that Plant Y will only bear fruit when the
period
of darkenss is 8 hours or less, it could not
have
born fruit in greenhouse 1. However, if Plant
Z
will only form flowers and seeds when exposed
to
days of no more than 15 hours in length, it
cer-
tainly could not have been native in areas
simu-
lated by greenhouses 2 and 3.
212.
A.
Blood is composed of cells and
plasma.
Plasma constitutes about 55% of blood
volume,
and cellular elements about 45%. The normal
red
blood cell hematocrit is about 36–45%.
Hemoglo-
bin, a complex molecule of iron and protein, is
a
key element of the RBC; the RBC carries
oxygen
from the lungs to the tissues and transports
carbon
dioxide from the tissues to the lungs. In the
break-
down of hemoglobin, bilirubin is excreted
and
iron is retained. The purpose of the
experiment
was to test the effect of different storage
condi-
tions on hemoglobin composition as revealed
by
gel electrophoresis. Although none of the
storage
conditions were able to maintain hemoglobin
in
an absoutely unchanged state, storage at
–20°C in
glycerol allowed the least change from the
fresh
configuration.
213.
C.
The suppressed plasma levels of FSH
and
LH during the follicular phase of the
menstrual
cycle are due to the negative inhibitory
effects of
estrogen being secreted from developing
follicles.
The small, abrupt rise in plasma estrogen
is
believed to trigger the ovulatory LH surge
(by
suspension of negative or positive feedback).
Dur-
ing the luteal phase, estrogen and
progesterone
again establish the negative-feedback
suppression
and luteal failure occurs on day 26. The
higher
levels of bound LH in the treated animals
indicate
that these animals had lower LH levels; the
drug
seems to inhibit LH release.
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