Biomedical subjects

L Myatt

Publications and source records attributed to L Myatt.

At least 37 records · Page 2Linked to original sources

PubMed1998

Increased nitrotyrosine in the diabetic placenta: evidence for oxidative stress.

OBJECTIVE: To evaluate the presence of nitrotyrosine (NT) residues in placental villous tissue of diabetic pregnancies as an index of vascular damage linked to oxidative stress. RESEARCH DESIGN AND METHODS: Villous tissue was collected and flash frozen after delivery from 10 class C and D IDDM patients (37.9+/-3.2 weeks) and 10 normotensive pregnant individuals (37.5+/-3.8 weeks). Serial sections of tissue were immunostained with specific antibodies to NT, endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and manganese superoxide dismutase (MnSOD). Sections were scored for intensity of immunostaining (0-3) by three observers blinded to the identity of tissue. RESULTS: All tissues demonstrated immunostaining for eNOS in both syncytiotrophoblast and stem villous vascular endothelium with no apparent differences between groups. Immunostaining for iNOS was seen in the villous stroma, but again was not different between the two groups. Significantly more intense NT staining was apparent in vascular endothelium and villous stroma (both P < 0.02) of diabetic placentas. The endothelium of large villous vessels of diabetic tissues also showed more intense immunostaining for MnSOD (P < 0.01). CONCLUSIONS: In these diabetic pregnancies, we were unable to show increased eNOS, unlike previous findings in preeclamptic pregnancies. The presence of NT may indicate vascular damage in the diabetic placenta due to peroxynitrite action formed from increased synthesis/interaction of nitric oxide and superoxide. The apparently paradoxical increase in MnSOD expression may be an adaptive response to increased superoxide generation.

Biomarkers↗

PubMed1997

Comparative localization of endothelial and inducible nitric oxide synthase isoforms in haemochorial and epitheliochorial placentae.

The presence and immunolocalization of type II (inducible or macrophage) and type III (endothelial) nitric oxide synthase (NOS) isoforms were compared in the term placentae of humans, rhesus monkeys, baboons, guinea-pigs, rats and sheep using isoform specific antibodies. In the human placenta, intense immunohistochemical staining for type III NOS was seen in syncytiotrophoblast with weaker staining in vascular endothelial cells. Only vascular endothelial cells showed positive III NOS staining in rhesus monkey, baboon, guinea-pig, rat and sheep placentae. No positive type III NOS immunostaining was seen in trophoblast from any non-human placentae. Western blotting revealed a 135-kDa type III NOS species in placental homogenates, semi-purified by ADP-sepharose affinity chromatography, from all the species tested confirming antibody specificity. Type II NOS immunostaining was localized to certain villous stromal cells which also stained for CD14 (a monocyte/macrophage marker) in the placenta of humans, rhesus monkeys, baboons and sheep. No specific immunohistochemical staining for type II NOS or CD14 was noted in the two rodent species, guinea-pig and rat. On Western blots, a 130-kDa type II NOS species was identified in semi-purified placental homogenates of every species except guinea-pig, although weak bands were seen for rhesus monkey and baboon. The failure of the antibodies to show type II NOS in the rat placenta by immunohistochemistry may be due to a difference in antigen conformation from Western blots. As only human placental syncytiotrophoblast expresses type III NOS, the putative functions ascribed to this isoform in syncytiotrophoblast, i.e., to prevent platelet and leucocyte aggregation in the intervillous space and adhesion to the trophoblast surface or to mediate peptide hormone release from trophoblast, may be unique to humans. Alternatively, syncytiotrophoblast-derived NO may fulfill some other unknown function. The similar pattern of expression of type II NOS in those species with villous fetomaternal interdigitation and multivillous fetomaternal blood flow interrelations may represent a more universal role in surveillance and/or protection against maternal insults or pathogens by immunologic activation and subsequent synthesis of nitric oxide which exerts a cytostatic/cytotoxic response.

Animals↗

PubMed1997

Changes in activity of cytosolic phospholipase A2 in human amnion at parturition.

OBJECTIVE: The purpose of this study was to determine whether increased cytosolic phospholipase A2 activity mediated arachidonic acid mobilization for prostaglandin synthesis in amnion at parturition. STUDY DESIGN: Amnion was collected immediately after delivery from four groups of patients: preterm (<37 weeks) with no labor or labor and term (>37 weeks) with no labor or labor and stored at -70 degrees C. Tissues were homogenized and centrifuged for 1 hour at 100,000 g, and cytosol was assayed for cytosolic phospholipase A2 activity with use of carbon 14-labeled 1-stearoyl-2 arachidonyl phosphatidylcholine plus 10 micromol/L unlabeled substrate and 5 mmol/L calcium in 10 mmol/L N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid, pH 7.4. Incubations were performed in duplicate +/- 10 micromol/L arachidonyl trifluoromethyl ketone, a specific inhibitor of cytosolic phospholipase A2 activity, at 30 degrees C for 45 minutes. RESULTS: Total cytosolic phospholipase A2 activity (in picomoles of arachidonic acid per minute per milligram of protein) calculated as the difference between the activity in the presence and absence of arachidonyl trifluoromethyl ketone was (mean +/- SE) as follows: preterm no labor (n = 7) 8.94 +/- 3.08, preterm with labor (n = 6) 6.79 +/- 2.31, term no labor (n = 7) 14.85 +/- 1.66, and term with labor (n = 5) 5.51 +/- 1.52. Enzyme activity increased with gestational age and was highest in the term no labor group. A significant decrease in cytosolic phospholipase A2 activity occurred with labor (p < 0.05). The greatest decrease in activity was in the term group (p < 0.05). CONCLUSION: Total cellular cytosolic phospholipase A2 activity in amnion is highest in anticipation of labor but during labor total activity is depleted, resulting in the low activity measured after delivery of the placenta. The substrate specificity and changes in amnion total cytosolic phospholipase A2 activity with labor strongly suggests a role in mediation of arachidonic acid mobilization and prostaglandin synthesis at labor.

Amnion↗

PubMed1997

Immunohistochemical localization of phospholipase A2 isoforms in human myometrium during pregnancy and parturition.

OBJECTIVE: The purpose of this study was to localize secretory phospholipase A2 and cytosolic phospholipase A2 isoforms in pregnant human myometrium and to determine changes in expression with gestational age or parturition. STUDY DESIGN: Myometrium was collected at cesarean section at term (>37 weeks) or preterm (<37 weeks) from patients who were or were not in labor (n = 5 each group). Frozen sections were incubated with specific monoclonal antibodies against secretory phospholipase A2 or cytosolic phospholipase A2 and immunostaining visualized with the Vectastain ABC method. The intensity of immunostaining in different cellular localizations was scored by an investigator blinded to tissue identity and compared among tissues with use of the Mantel-Haenszel chi2 test. RESULTS: Secretory phospholipase A2 immunostaining was dispersed in the perinuclear region throughout the myometrial smooth muscle fibers and in vascular smooth muscle. Cytosolic phospholipase A2 immunostaining was predominantly localized to endothelial cells of myometrial blood vessels and weakly throughout myometrial fibers. There was no apparent change in intensity of immunostaining for either isoform with gestational age or with the absence or presence of labor. CONCLUSION: The differential localization of the two phospholipase A2 isoforms suggests different functions. The apparent lack of change in expression during late gestation or with labor possibly suggests changes in myometrial phospholipase A2 activity and hence local myometrial arachidonic acid mobilization and presumably prostaglandin synthesis may not be associated with the onset of or maintenance of parturition.

Female↗

PubMed1997

Inducible (type II) nitric oxide synthase in human placental villous tissue of normotensive, pre-eclamptic and intrauterine growth-restricted pregnancies.

We have utilized two distinct monospecific antibodies against the type II (macrophage or inducible) nitric oxide synthase (NOS) isoform to localize the distribution of the enzyme within the human placenta in tissues from normotensive pregnancies and those complicated by pre-eclampsia and/or intrauterine growth restriction. Both antibodies immunolocalize to cells in the villous stroma on frozen sections of villous tissue. Colocalization studies with anti-CD14 or anti-CD45 antibodies that recognize cells of leucocyte or monocyte/macrophage lineage indicate that Hofbauer cells are expressing type II NOS. This is in contrast to expression of type III (endothelial) NOS which is seen in syncytiotrophoblast and in villous vascular endothelium. In some, but not all, normotensive and pathologic placental tissue, some type II NOS immunostaining could be seen in syncytiotrophoblast and vascular endothelium; however, no differences could be discerned between groups of tissues. Expression of type II NOS by Hofbauer cells may indicate they are involved in surveillance against maternal immune insult or maternal pathogens whereby they secrete nitric oxide to exert a cytostatic/cytotoxic effect.

Female↗

PubMed1997

Endothelial nitric oxide synthase in placental villous tissue from normal, pre-eclamptic and intrauterine growth restricted pregnancies.

Nitric oxide (NO) regulates blood flow in the human placenta. As increased resistance to blood flow is seen in the fetal-placental vasculature in pregnancies complicated by pre-eclampsia and/or intrauterine growth restriction (IUGR), we examined expression of endothelial nitric oxide synthase (eNOS) in these placentas. Placental villous tissue sections were obtained from normotensive control (n = 5), IUGR alone (n = 5) or pre-eclamptic (with or without IUGR (n = 9) patients, immunostained for eNOS and scored for localization, type (punctate or diffuse) and intensity of eNOS staining in syncytiotrophoblast and placental vessels. The significance of differences was calculated using the Mann-Whitney U-test. No differences in intensity or type of immunostaining in syncytiotrophoblast were seen. Placentas from patients with pre-eclampsia with or without IUGR had a significantly more basal distribution of eNOS in syncytiotrophoblast. eNOS immunostaining was absent in terminal villous capillary and faint in stem villous vessel endothelium of normal placentas, but was intense in the endothelium of both of these types of vessels in the IUGR and pre-eclampsia groups, with significantly greater staining seen in stem vessels of patients with IUGR alone. This increased eNOS expression and hence increased NO production in the fetal-placental vasculature may be an adaptive response to the increased resistance and poor perfusion in these pathological pregnancies.

Adult↗

PubMed1997

Immunolocalization of the inducible nitric oxide synthase isoform in human fetal membranes.

PROBLEM: Nitric oxide (NO) synthesized by fetal membranes may protect the fetus from maternal infection or immune challenge or have a tocolytic effect on myometrium. The sites of synthesis and enzymes responsible for NO production in human fetal membranes remain unidentified. METHOD OF STUDY: Fetal membranes were obtained from four groups of patients: term (> 37 weeks gestation) or preterm (< 37 weeks gestation), both either in labor or not in labor. Frozen sections of membrane rolls were immunostained for inducible (iNOS) and endothelial (eNOS) nitric oxide synthase isoforms and the monocyte/macrophage marker CD14. RESULTS: Positive iNOS immunostaining was found in fibroblasts of amnionic and chorionic mesenchyme and in decidual macrophages identified by CD14 from all four groups of tissues. No iNOS immunostaining was seen in amnion epithelium or chorion trophoblast. Very intense iNOS staining was seen with evidence of monocyte/macrophage invasion of membranes. eNOS immunostaining was only found in decidual vascular endothelium. CONCLUSIONS: Constitutive expression of iNOS in decidual macrophages and fetal membrane fibroblasts may form an immune barrier against maternal insult. In chorioamnionitis, macrophage recruitment and NO expression may be part of the maternal immune response.

Endothelium, Vascular↗

PubMed1997

Nitric oxide synthase activity in umbilical and placental vascular tissue of gestational diabetic pregnancies.

OBJECTIVE: Nitric oxide (NO) synthase activity in the fetal-placental vasculature of gestational diabetic pregnancies was compared to non-diabetic controls. METHODS: Placentae were collected from non-diabetic deliveries (n = 5) and from patients with gestational diabetes (n = 8). Umbilical cord and chorionic plate arteries and veins and stem villous vessels were quickly dissected out, cleaned of contaminating tissue, snap frozen in liquid nitrogen and stored at -80 degrees C. NO synthase activity was measured in the homogenate of these vessels by the arginine to citrulline conversion assay using 5 microM 3H-L-arginine with 1 mM NADPH, 100 microM free calcium, 50 units/ml calmodulin, 10 microM tetrahydrobiopterin and 2 microM flavin adenine dinucleotide with 45-min incubation at 27 degrees C. Enzyme activity was expressed as picomoles of 3H-L-citrulline formed per milligram of protein per minute. RESULTS: No significant differences in NO synthase activity were found between non-diabetic and gestational diabetics for umbilical cord artery (0.58 +/- 0.22 vs. 0.19 +/- 0.06), cord vein (0.39 +/- 0.21 vs. 0.07 +/- 0.03), chorionic plate artery (0.32 +/- 0.14 vs. 0.26 +/- 0.19) or vein (0.41 +/- 0.15 vs. 0.22 +/- 0.06), respectively (mean +/- SEM). Significantly greater activity was found in stem villous vessels of non-diabetic placentae (5.64 +/- 2.0) compared to those of gestational diabetic placentae (0.48 +/- 0.19; p < 0.01). CONCLUSION: The reduced blood flow and increased vascular resistance observed in diabetic pregnancies may be due to decreased NO synthesis and activity in the stem villous vessels which are the major determinants of resistance in the fetal-placental vasculature.

Diabetes, Gestational↗

PubMed1997

Differential localization of superoxide dismutase isoforms in placental villous tissue of normotensive, pre-eclamptic, and intrauterine growth-restricted pregnancies.

Several isoforms of superoxide dismutase (SOD), including copper/zinc (cytosolic) and manganese (mitochondrial), exist. In the human placenta, SOD may prevent excessive superoxide accumulation and any potential deleterious oxidative effects. In pre-eclampsia, increased levels of lipid peroxide and decreased SOD activity have been described in the placenta. Oxidative stress such as occurs in pre-eclampsia can alter expression of SOD isoforms. The objective of this study was to localize the copper/zinc and manganese SOD isoforms in the placenta using immunohistochemistry and to compare localization and intensity of immunostaining in tissues from normotensive pregnancies with those from pregnancies complicated by pre-eclampsia and/or intrauterine growth restriction (IUGR). Western blotting with specific antibodies recognized a 17-kD copper/zinc and a 23-kD manganese SOD subunit in placental homogenates. Intense immunostaining for the manganese SOD isoform was seen in villous vascular endothelium, but only faint staining was found in the syncytiotrophoblast or villous stroma. In serial sections, intense immunostaining for copper/zinc SOD was seen in certain cells of the villous stroma but only faint immunostaining in syncytiotrophoblast and vascular endothelium. No apparent differences in localization or intensity of immunostaining for either isoform were seen between tissues of normotensive or pre-eclamptic pregnancies, with or without IUGR. The different cellular localizations of the SOD isoforms suggest that they fulfill different functional roles within the placenta.

Blotting, Western↗

PubMed1996

Induction of both cytosolic phospholipase A2 and prostaglandin H synthase-2 by interleukin-1 beta in WISH cells in inhibited by dexamethasone.

In previous studies we have shown that IL-1 beta induced both PGE2 release and total cellular cPLA2 activity and cPLA2 protein synthesis in human amnion-derived WISH cells. In this study, the effect of IL-1 beta on cPLA2 and PGHS-2 mRNA expression was investigated. Using RT-PCR, we found that IL-1 beta (0.1 ng/ml) coordinately induced both cPLA2 and PGHS-2 mRNA expression within 2 hours. The synthetic glucocorticoid dexamethasone (10(-10)-10(-6)M) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression activity and protein synthesis and PGE2 release in a concentration dependent manner. In the absence of IL-1 beta, dexamethasone alone (10(-6)M) inhibited basal cPLA2 activity, mRNA expression and protein synthesis. In addition, cycloheximide (5 micrograms/ml) apparently superinduced, but actinomycin D (2 micrograms/ml) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression suggesting that both are immediate early genes and a transcriptional mechanism is involved in the induction of both cPLA2 and PGHS-2 mRNA by IL-1 beta.

Amnion↗

PubMed1996

Elevation of nitrate levels in pregnant ewes and their fetuses.

OBJECTIVE: Nitric oxide is a potent vasodilator released by endothelial cells that may play an important role in modulating maternal and fetal vascular tone in normal pregnancy. The current study was designed to evaluate whether plasma or urine nitrite and nitrate (the metabolites of nitric oxide) concentrations are elevated in pregnant compared with those of nonpregnant sheep and whether the nitrate concentrations in the fetal circulation were increased in comparison with the maternal circulation. STUDY DESIGN: Eleven pregnant sheep and seven nonpregnant oophorectomized sheep were instrumented with catheters in the maternal and fetal femoral arteries and veins, uterine and umbilical veins, and amniotic cavity. Blood, urine, and amniotic fluid samples were collected for nitrate determination at least 5 days after surgery. After extraction nitrate was reduced to nitrite and quantitated with the Greiss reagent. RESULTS: Arterial plasma nitrate concentrations in the pregnant sheep were significantly elevated compared with those of nonpregnant sheet (5.0 +/- 0.9 vs 2.5 +/- 0.6 micromol/L, p < 0.05). The urinary nitrate concentrations were also significantly increased in the pregnant sheep compared with those of nonpregnant sheet (89.9 +/- 16.3 vs 23.1 +/- 4.5 nmol/mg creatinine, p < 0.01). Fetal plasma nitrate concentrations were ninefold higher than the maternal nitrate concentrations (43.9 +/- 7 vs 5.0 +/- 0.9 micromol/L, p < 0.01), whereas amniotic fluid concentrations were extremely high (133.8 +/- 13.8 micromol/L, n = 3). No venous-arterial differences were measurable across either the maternal or fetal sides of the placenta. CONCLUSION: Nitrate concentrations in pregnant sheet and their fetuses are increased. The increased nitrate concentrations in the maternal and fetal circulations may reflect the increased nitric oxide synthesis, which may in part mediate the cardiovascular adaptations to normal pregnancy and the low systemic and umbilical vascular resistance in the fetus.

Amniotic Fluid↗

PubMed1996

Decreased nitric oxide production following extremity ischemia and reperfusion.

BACKGROUND: Nitric oxide (NO), the endogenous vasodilator, is an important regulator of vascular tone. We investigated NO production following lower extremity ischemia. METHODS: Rabbits underwent 6 hours of bilateral leg ischemia followed by unrestricted reperfusion. Physiologic parameters were continuously measured and blood was assayed for NO2 and NO3. RESULTS: Acute ischemia of the lower extremities produced an immediate increase in mean arterial blood pressure while later reperfusion induced a significant decrease (P < 0.0005). There was a fall in femoral blood flow during reperfusion. NO2/ NO3 concentrations decreased significantly to 89% of baseline values after ischemia and 77% after 1 hour of reperfusion (P < 0.005). A significantly higher mortality was found in association with decreased NO2/NO3 concentrations. CONCLUSIONS: Nitric oxide appears to be a regulator of regional blood flow during reperfusion following extremity ischemia. Decreased NO production may contribute to impaired regional blood flow and mortality.

Animals↗

PubMed1996

Nitrotyrosine residues in placenta. Evidence of peroxynitrite formation and action.

The interaction of nitric oxide and superoxide produces peroxynitrite anion, a strong, long-lived oxidant with pronounced deleterious effects that may cause vascular damage. The formation and action of peroxynitrite can be detected by immunohistochemical localization of nitrotyrosine residues. We compared the presence and localization of nitrotyrosine and of the endothelial isoform of nitric oxide synthase in placental villous tissue from normotensive pregnancies (n = 5) with pregnancies complicated by preeclampsia (n = 5), intrauterine growth restriction (n = 5), and preeclampsia plus intrauterine growth restriction (n = 4), conditions characterized by increases in fetoplacental vascular resistance, fetal platelet consumption, and fetal morbidity and mortality. In all tissues, absent or faint nitrotyrosine immunostaining but prominent nitric oxide synthase immunostaining were found in syncytiotrophoblast. In tissues from normotensive pregnancies, faint nitrotyrosine immunostaining was found in vascular endothelium, and nitric oxide synthase was present in stem villous endothelium but not in the terminal villous capillary endothelium. In contrast, in preeclampsia and/or intrauterine growth restriction, moderate to intense nitrotyrosine immunostaining was seen in villous vascular endothelium, and immunostaining was also seen in surrounding vascular smooth muscle and villous stroma. The intensity of nitrotyrosine immunostaining in preeclampsia (with or without intrauterine growth restriction) was significantly greater than that of controls. Intense nitric oxide synthase staining was seen in endothelium of stem villous vessels and the small muscular arteries of the terminal villous region in these tissues and may be an adaptive response to the increased resistance. The presence of nitrotyrosine residues, particularly in the endothelium, may indicate the formation and action of peroxynitrite, resulting in vascular damage that contributes to the increased placental vascular resistance.

Adult↗

PubMed1995

The action of two natriuretic peptides (atrial natriuretic peptide and brain natriuretic peptide) in the human placental vasculature.

OBJECTIVE: Our purpose was to compare the actions of atrial natriuretic peptide and brain natriuretic peptide in the human placental vasculature. STUDY DESIGN: Isolated placental cotyledons were dually perfused with fetal perfusion pressure used as an index of vascular response. The effect of angiotensin II (10(-10) to 10(-6) mol/L bolus injection) was established in the absence or presence of atrial natriuretic peptide (10(-8) mol/L) or brain natriuretic peptide (10(-8) mol/L final concentration). The role of nitric oxide as a mediator of natriuretic peptide action was investigated by perfusion of n-nitro-L-arginine (10(-3) mol/L), an inhibitor of nitric oxide synthase. Attenuation of the action of atrial natriuretic peptide by placental peptidases was studied by perfusion with the peptidase inhibitor benzamidine (2 x 10(-2) mol/L). Statistical significance was determined by analysis of variance and paired t test. RESULTS: Significant attenuation of vasoconstrictor responses to angiotensin II occurred within both atrial natriuretic peptide and brain natriuretic peptide; however, brain natriuretic peptide was more effective. n-Nitro-L-arginine did not affect the attenuation of angiotensin II-induced vasoconstriction by atrial or brain natriuretic peptides. In the presence of benzamidine atrial natriuretic peptide exerted a significantly greater vasodilator effect. CONCLUSION: Brain natriuretic peptide is a more potent vasodilator of the placental vasculature than is atrial natriuretic peptide. The low efficacy of atrial natriuretic peptide may be related to placental peptidases. Nitric oxide does not mediate the action of atrial natriuretic peptide or brain natriuretic peptide.

Angiotensin II↗

PubMed1995

The interaction of nitric oxide and superoxide in the human fetal-placental vasculature.

OBJECTIVE: Our purpose was to study the interaction of nitric oxide and superoxide anion on the vasculature of the isolated perfused human placental cotyledon. STUDY DESIGN: Isolated placental cotyledons were preconstricted with the thromboxane mimetic U46619, and fetal perfusion pressure was used as an index of response. The interaction of nitric oxide and O2- was studied by three protocols: (1) with endogenous nitric oxide, (2) with addition of exogenous nitric oxide, and (3) with inhibition of nitric oxide synthesis by the nitric oxide synthase inhibitor N-nitro-L-arginine. O2- was generated by infusion of purine-xanthine oxidase. Statistical significance of response to treatment was determined by paired t test. RESULTS: Infusion of xanthine oxidase with purine in the presence of endogenous nitric oxide resulted in vasodilation (p < 0.05). Vasodilation was more pronounced in the presence of exogenous nitric oxide (p < 0.008). Coinfusion of xanthine oxidase with purine in the presence of N-nitro-L-arginine to inhibit nitric oxide synthesis resulted in vasoconstriction. CONCLUSION: We conclude that, rather than superoxide inactivating nitric oxide, interaction of the two radicals generates in the placental vasculature a vasodilator, which may be peroxynitrite.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed1995

Immunohistochemical characterization of placental nitric oxide synthase expression in preeclampsia.

OBJECTIVE: Our purpose was to compare the expression of endothelial nitric oxide synthase in the placenta and umbilical cord of preeclamptic placenta with that of the normotensive placenta. STUDY DESIGN: We compared placental endothelial nitric oxide synthase expression in preeclamptic (n = 3) with that in normal (n = 3) pregnancies. Frozen sections of umbilical cords, chorionic plate vessels, and terminal villi were immunostained with a monoclonal endothelial nitric oxide synthase antibody (H32). RESULTS: No difference in endothelial nitric oxide synthase immunostaining in the endothelium of the umbilical cord artery and vein, chorionic plate vessels, and stem villous vessels was found between preeclamptic and normotensive pregnancies. In contrast, in the preeclamptic placentas endothelial nitric oxide synthase immunostaining was seen in the small terminal villous vessels with underlying smooth muscle layer. In the syncytiotrophoblast endothelial nitric oxide synthase immunostaining appeared primarily apical in location and diffuse in distribution in the preeclamptic placentas but primarily basal and punctate in the normotensive placentas. CONCLUSIONS: Differences in endothelial nitric oxide synthase expression in terminal villous vessels and in syncytiotrophoblast may be a result of vascular alterations or damage that take place in the placenta in preeclampsia. These differences may alter the regulation of blood flow in the fetal and maternal placental vasculatures in preeclampsia.

Antibodies, Monoclonal↗

PubMed1995

Shear stress may stimulate release and action of nitric oxide in the human fetal-placental vasculature.

OBJECTIVE: Our purpose was to determine the effect of perfusate flow or viscosity on release and action of nitric oxide in the human fetal-placental vasculature in vitro. STUDY DESIGN: Cotyledons from normal term placentas were perfused with Hanks' buffered saline solution gassed with 95% oxygen and 5% carbon dioxide, pH 7.4, at 37 degrees C with a maternal flow rate of 10 ml/min. Fetal flow rate was varied from 1 to 10 ml/min at 10-minute intervals (n = 6), and perfusion pressure was recorded. Viscosity was varied by perfusion of both circulations with Hanks' balanced salt solution containing 0, 2.5, 5.0, 7.5, or 10% dextran, the concentration being changed every 20 minutes and pressure recorded at fetal flow rates of 4 (n = 4) or 1 ml/min (n = 7). All experiments were performed in the presence or absence of the nitric oxide synthase inhibitor N-nitro-L-arginine (10(-3) mol/L) in the same placentas. Data were analyzed by analysis of variance with repeated measures. RESULTS: Increasing fetal flow rate with or without N-nitro-L-arginine resulted in a significant increase in perfusion pressure (p = 0.0011). Addition of N-nitro-L-arginine gave an overall significant increase in perfusion pressure (p = 0.0048). At a fetal flow rate of 4 ml/min increasing dextran concentration with or without N-nitro-L-arginine gave a significant increase in perfusion pressure (p = 0.0011), but the increase in perfusion pressure in the presence of N-nitro-L-arginine did not reach significance (p = 0.06). At 1 ml/min increasing dextran concentration resulted in a significant increase in fetal perfusion pressure (p = 0.001), but no significant effect of N-nitro-L-arginine was observed. CONCLUSION: Altering shear stress by increasing fetal flow rate or viscosity of the medium may increase synthesis and release of nitric oxide, which attenuates increases in perfusion pressure.

Arginine↗

PubMed1995

Interaction of angiotensin II and brain natriuretic peptide in the placentas of normal and diabetic women.

OBJECTIVE: To evaluate the effects of angiotensin II and brain natriuretic peptide on the placental vasculature of diabetic women. METHODS: Term placentas from five diabetic women and five nondiabetic controls were collected. Isolated placental cotyledons were perfused dually with fetal perfusion pressure as an index of vascular response. The effect of angiotensin II (10(-10)-10(-5) mol/L bolus injection) was established in the fetal-placental vasculature of all placentas in the absence or presence of brain natriuretic peptide (10(-8) mol/L final concentration). Data were analyzed using repeated measures analysis of variance and paired t test where appropriate. RESULTS: A significant vasoconstrictor response to angiotensin II was achieved in placentas of both diabetic and nondiabetic women (P < .001); however, the angiotensin II-induced increase in perfusion pressure was significantly greater in the diabetic group (P < .01). Significant attenuation of vasoconstrictor response to angiotensin occurred in the presence of brain natriuretic peptide in placentas of both nondiabetic (P < .0025) and diabetic (P < .025) women, but the effect was more prominent in the diabetic group. CONCLUSION: The in vitro placental vasculature of diabetic women is more sensitive to angiotensin II than is the in vitro placental vasculature of nondiabetic women. The attenuation exerted by brain natriuretic peptide on angiotensin II-induced vasoconstriction is more prominent in placentas from diabetic women compared to those from nondiabetic women.

Adult↗