The Medical College - Page 51
striations are produced by the arrangement
within the
fibril of myofilaments; myosin is the thick
myofilament,
whereas actin is considered the thin
myofilament.
179.
A sarcomere is the area between:
A.
two A bands.
C.
two I bands.
B.
two H bands.
D.
two Z bands.
180.
During contraction the lengths of the thick
and
thin myofilaments:
A.
increase.
B.
decrease.
C.
remain the same.
D.
first increase, then decrease.
181.
If we could imagine observing a muscle
contrac-
tion under a light microscope, we would see
the
narrowing of the:
A.
H and I bands.
C.
Z bands.
B.
A bands.
D.
H bands only.
182.
If the muscle were deprived of ATP, which of
the
following would NOT be affected?
A.
the sodium pump of the muscle
membrane
B.
the calcium pump of the
sarcoplasmic
reticulum
C.
the length of the myosin filaments
D.
the velocity of shortening
183.
What is the internal activator substance that
is
released during excitation--contraction
cou-
pling?
A.
ATP
C.
Ca
2+
B.
Mg
2+
D.
H
+
Passage VII (Questions
184–189)
During the inflammatory reaction, immune
and
paraimmune system cells circulating in
microvessels
adhere to the endothelium of these vessels in
areas of
tissue injury. The adherent cells then migrate
across the
endothelium into the injured tissue. The
adherence of
the cells to the endothelium is stimulated by
cytokines
such as tumor necrosis factor, TNF. The immune
and
paraimmune system cells may adhere to
endothelial
cells through binding of CD-18 molecules on the
sur-
faces of the immune and paraimmune system cells
to
GMP-140 glycoproteins on the surfaces of
endothelial
cells. A series of experiments to evaluate
these
hypotheses is shown in figures 1–3. Figure
1 reports
the binding of neutrophils, monocytes, and
lympho-
cytes to plastic dishes coated with varying
amounts of
GMP-140. Figure 2 shows neutrophil adhesion to
plas-
tic dishes under varying conditions. Figure 3
shows
neutrophil adhesion to cultured layers of
vascular
endothelial cells in the presence of varying
concentra-
tions of GMP-140 in the test
solution.
Figure 1
Adherence of neutrophils (v), monocytes (q), and lympho-
cytes (s) to plastic dishes that had been
coated with varying
anounts of GMP-140.
Figure 2
Effects of pretreatment of plastic dishes or
neutrophils on the
attachment of neutrophils to plastic
dishes.
1--neither cells nor dish were
pretreated
2--dish coated with GMP-140; no treatment of
cells
3--dish coated with GMP-140 then treated with
rabbit anti-
bodies, which bind to GMP-140
4--dish coated with GMP-140 then treated with
rabbit anti-
bodies, which do not bind to
GMP-140
5--dish coated with GMP-140; cells treated with
antibodies,
which bind to CD-18
6--dish coated with GMP-140; cells treated with
antibodies,
which do not bind to CD-18
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