Biomedical Engineering Reference
In-Depth Information
2.8 ATA
Room air
Room air
400
200
0
2000
1000
0
0
30
40
50
10
20
Time (min)
FIGURE 1.11
NO concentration (top) and O
2
concentration (bottom) as a function of O
2
pressure. As can
be seen, NO and O
2
concentrations increase signifi cantly when a rat is exposed to pressurized O
2
atmospheres
(2.8 atmospheres absolute, ATA). (Reprinted with permission from the American Physiological Society [127].)
NO was indeed being detected in the subjects. The same group used a similar experi-
mental design to monitor NO concentration, as well as SkBF, during reactive hyperemia
under the human skin [126].
Thom and coworkers published results on the stimulation of perivascular NO synthe-
sis by oxygen [127]. To perform this study a 200
m diameter electrode (ISONOP200)
was placed between the aorta and vena cava of anesthetized rats and mice (rodents) and
then the rodents were placed inside a hyperbaric chamber. Inside the hyperbaric cham-
ber the partial pressure of O
2
was regulated/changed as NO concentration was moni-
tored. Figure 1.11 shows that NO concentration increased as a function of O
2
partial
pressure. This experiment is important for understanding how NO synthesis, by NOS,
is altered and regulated by O
2
.
Studies have also been conducted on the NO release from plants and the effects of
a plant diet on atherosclerosis and endothelial cell dysfunction. Visioli and coworkers
studied the effects that a diet of wild artichoke and thyme had on the release of NO
from porcine aortic endothelial cells and cerebral cell membranes [118]. For this study
a rat brain was homogenized and cell membranes isolated by ultracentrifugation and NO
release monitored using a 2 mm nitric oxide sensor (ISONOP). The cell membranes were
then exposed to wild artichoke and thyme extracts. This study showed that NO release
was signifi cantly increased following wild artichoke and thyme extract addition. These
results suggest that eating a diet rich in phenolic compounds, such as wild artichoke and
thyme, contributes to maintenance of a healthy cardiovascular system. Yamasaki and
coworkers used an ISONOP from WPI to study the ability of plant nitrate reductase to
produce NO [117]. Figures 1.12 and 1.13 show that plant nitrate reductase produces NO
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