Article Abstract:
Taking a small sample of uterine tissue at the time of a cesarean delivery does not adversely affect the woman, according to a study of 118 women who had this procedure and 236 who did not. Uterine tissue samples are needed for research purposes to determine exactly how the uterus changes during labor.
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Article Abstract:
Atrial natriutic peptide (ANP) and brain natriuretic peptide (BNP) both appear to play a role in dilating placental blood vessels but BNP is more powerful. Neither one works by stimulating production of nitric oxide. Placental cotyledons from fresh placentas were catheterized on both the maternal and fetal sides. Fetal perfusion pressure was used as an indicator of blood vessel response. The effect of angiotensin II, a potent blood vessel constrictor, was measured in the absence or presence of ANP or BNP. Both ANP and BNP acted as dilators, but BNP was more potent. Inhibiting the production of nitric oxide did not reduce the dilating effect of either natriuretic peptide. The potency of ANP was increased when an inhibitor of placental peptide enzymes was added. This suggests that the reason BNP acts as a more potent dilator may be that ANP is selectively degraded by placental peptide enzymes.
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Article Abstract:
Nitrous oxide appears to interact with O2-, producing peroxynitrite, which dilates blood vessels. Human placentas were placed in a bath and tubes were inserted into blood vessels on both the fetal and maternal sides. The effect of various chemicals on blood vessel dilation or constriction could be evaluated by recording changes in perfusion pressure as they were infused into the blood vessels. Blood vessels were first constricted. The effect of nitric oxide was evaluated both alone and in the presence of O2-. Adding nitric oxide increased blood vessel dilation. Dilation was inhibited by a nitric oxide inhibitor, suggesting that nitric oxide is involved in dilation. O2- had no dilation effect when nitric acid production was inhibited. Nitric oxide with O2- had a stronger effect than nitric oxide alone, suggesting that a reaction product of the two, peroxynitrite, is a dilating agent.
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