| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Regular Articles |
From the Magee-Women’s Research Institute and Department of
Obstetrics, Gynecology and Reproductive Sciences,*
University of Pittsburgh, Pittsburgh, Pennsylvania; and the
Departments of Stomatology
and of
Anatomy, Pharmaceutical Chemistry, and Obstetrics, Gynecology and
Reproductive Sciences,
University of
California at San Francisco, San Francisco, California
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Xanthine oxidase, which metabolizes xanthine and hypoxanthine to uric acid with production of superoxide and hydrogen peroxide, is an integral mediator of reactive oxygen species generation in many settings. Usually, this enzyme is present as the holoenzyme xanthine dehydrogenase/xanthine oxidase (XDH/XO). The dehydrogenase isoform (XDH) converts purines to uric acid with reducton of nicotinamide-adenine dinucleotide (NAD) to reduced NAD (NADH). With hypoxia and in response to several cytokines, XDH/XO synthesis increases, and the conversion of the enzyme to the XO form is enhanced.9 Reduced organ perfusion and subsequent reperfusion are proposed to result in increased XO during reduced flow and in subsequent formation of reactive oxygen species with reperfusion. The inadequate placental perfusion that characterizes preeclampsia is believed to reduce oxygen delivery to the placenta. Vasospasm may result in intermittent variations of utero-placental perfusion during preeclampsia. Hence, although it is unclear whether postischemic reoxygenation occurs in the preeclampsia placenta, we proposed that XO might be a source of reactive oxygen species in the disorder.
In previous studies, we documented that XO, which was thought to be absent from the placenta,10 was present and active.11 In this study, we examined XDH/XO protein expression and activity in placental villi and placental bed biopsies from normal and preeclamptic women. We also studied expression (at the protein level) of enzymes that degrade superoxide (copper, zinc-superoxide dismutase (SOD); CuZn-SOD) and hydrogen peroxide (catalase). We looked for evidence of enhanced immunoreactive nitrotyrosine in placentas from women with preeclampsia, an oxidative change suggestive of interaction of O2.- with nitric oxide (NO) to form a peroxynitrite anion (ONOO-). We report that invasive cytotrophoblasts from preeclamptic women manifest increased amounts and activity of XDH/XO accompanied by reduced expression of the buffering enzyme SOD but no reduction in catalase and that the cells show increased nitration of tyrosine indicative of oxidative modification.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Subjects in these studies were cared for at Moffitt Hospital and San Francisco General Hospital, University of California at San Francisco (San Francisco, CA); at Magee-Women’s Hospital, University of Pittsburgh (Pittsburgh, PA); and at the University of Tennessee Medical Center (Memphis, TN). The study was approved by the institutional review boards of the participating institutions.
Preeclampsia was diagnosed by similar criteria at all institutions. The diagnosis required gestational hypertension, proteinuria, hyperuricemia, and reversal of hypertension and proteinuria after pregnancy.12 Hypertension was defined as an increase of 30 mmHg systolic or 15 mmHg diastolic blood pressure as compared with values obtained before 20 weeks of gestation or an absolute blood pressure >140/90 mmHg. Proteinuria was defined as >500 mg/24-hour collection or >2+ on voided or 1+ on catheterized random urine specimens. Hyperuricemia was defined as >1 SD above usual values at the time of gestation. Chronic hypertensive women or those with other medical complications were excluded. Women in the control group had normal blood pressure and no other medical complications.
Tissue Processing
Samples of floating villi and basal plate for immunofluorescence staining were obtained from elective terminations and at the time of term cesarean section and vaginal delivery (Moffitt Hospital and San Francisco General Hospital). Tissue biopsy and preparation for immunostaining were as described previously.13,14 Placental villi (from Magee-Women’s Hospital) and placental site curettings (from University of Tennessee Medical Center) for determining XDH/XO activity were obtained after separation of the placenta, immediately frozen in liquid nitrogen, and stored at -80°C until further processing. In this case, placental samples were obtained only from women delivered by cesarean section without prior contractions. This eliminated any potential influence of uterine contraction on XDH/XO activity. The placental bed was sampled by sharp curetting of the uterine site to which the placenta was attached.
Immunohistochemical Staining
Primary Antibodies
Immunostaining used specific antibodies to XO (rabbit polyclonal immunoglobulin G (IgG), 1:3000 dilution; Rockland, Gilbertville, PA), nitrotyrosine (mouse monoclonal IgG, 1:100 dilution; from J. S. Beckman, University of Alabama, Birmingham, AL, and subsequently from Upstate Biotechnology, Inc., Lake Placid, NY), Cu,Zn-SOD (mouse monoclonal IgG, 1:500 dilution; Sigma Chemical Co., St. Louis, MO), catalase (rabbit polyclonal IgG, 1:100 dilution; from P. B. Lazarow, Mount Sinai Medical Center, New York, NY), and cytokeratin (rat monoclonal IgG, 1:200 dilution14 ).
Specimens and Antibody Localization
Double indirect immunofluorescence was used to localize the primary antibody. Sections of floating villi, basal plate, and placental bed were exposed to an appropriate dilution of primary antibodies for 60 minutes. Negative-control incubations omitting either the primary or secondary antibodies were routinely performed. We always stained with only one antibody (either anti-cytokeratin or the experimental reagent) to eliminate red/green crossover. No nonspecific contribution to staining intensity was observed. For catalase, specificity was confirmed by using equal dilutions of rabbit pre-immune sera in place of the primary antibody as a negative control. Specificity of anti-XO and nitrotyrosine immunostaining was confirmed using equivalent dilutions of antigen-preabsorbed antibodies. Tissues were incubated for 30 minutes with fluorescein- and rhodamine-conjugated secondary antibodies.14 Sections were viewed with a Zeiss Axiophot Epifluorescence microscope equipped with filters to selectively view the rhodamine and fluorescein images without cross contamination.
Control specimens (10) were obtained at the following gestational ages:
7 weeks (1 sample obtained at the time of pregnancy termination), 15
weeks (1 sample obtained at the time of pregnancy termination), 18
weeks (2 samples obtained at the time of pregnancy termination), 26
weeks (2 samples–one obtained from a woman who delivered due to
cervical incompetence and another obtained after termination of a
pregnancy due to inoperable conjoined twins). The remainder of the
samples were obtained from control nulliparous women who underwent
cesarean sections at the following gestational ages: 33 weeks (1
sample), 34 weeks (1 sample), and 38 weeks (2 samples). None of the
control patients had evidence of preeclampsia, gestational
hypertension, chorioamnionitis, or chronic hypertension. Likewise, none
had a medical history that suggested they were at risk for developing
preeclampsia. We also obtained 10 specimens from patients with
preeclampsia as follows: 24 weeks (1 sample), 26 weeks (2 samples), 28
weeks (2 samples), 32 weeks (2 samples) 33 weeks (1 sample), 35 weeks
(1 sample), and 38 weeks (1 sample). In all cases, sections from three
different biopsy sites within the placental bed were examined. Clinical
characteristics of patients are summarized in Table 1
. An atheromatous coronary artery
specimen (provided by S. C. Watkins, Department of Cell Biology
and Physiology, University of Pittsburgh) from a 73-year-old female who
died of aortic aneurysm was used as a positive control tissue for
anti-nitrotyrosine immunostaining. This vessel showed nitrotyrosine
staining in atheroma and foam cells (but not the underlying smooth
muscle).
|
Materials
[14C] Xanthine, specific activity 55 Ci/mmol, was purchased from Dupont-NEN, Boston, MA. All other materials were purchased from Sigma.
Tissue Preparation
For XDH/XO analyses, clinical characteristics of patients from
whom samples were obtained are summarized in Table 2
. Approximately 0.5 g of tissue was
frozen in liquid nitrogen and ground into powder. Cold buffer (50
mmol/L potassium phosphate, 10 mmol/L dithiothreitol, 1 mmol/L
phenylmethyl sulfonyl fluoride, 0.1 mmol/L ethylenediaminetetraacetic
acid, pH 7.8) was added to the powder (1:5 w/v). The slurry was
centrifuged at 40,000 x g for 30 minutes at 4°C, and
the supernatant was applied to a G-25 Sephadex column at 4°C to
eliminate endogenous xanthine and low-molecular-weight inhibitors. The
excluded volume was collected for assay. No more than 60 minutes
elapsed from the beginning of the tissue processing to the beginning of
the activity assay.
|
The XDH/XO enzyme assay was performed as previously described.11,15 Briefly, total XDH/XO activity was determined by the conversion of [14C] xanthine to [14C] uric acid. The reaction mixture contained NAD (500 µmol/L), [14C] xanthine (34 µmol/L), and sample in a total volume of 175 µl. To eliminate inhibition by accumulation of NADH, lactate dehydrogenase (5 U/ml) and pyruvate (5 mmol/L) were added. In this system, NADH is continuously converted to NAD. The proportions of enzyme in the different isoforms were evaluated by comparing [14C] uric acid production in the presence (XDH/XO) and absence (XO) of NAD. The mixture was incubated for 90 minutes, and the reaction was terminated by adding 25 µl of 40% trichloroacetic acid and centrifuging for 7 minutes at 16,000 x g. The reaction was linear for at least 120 minutes. The supernatant (175 µl) was applied to a 1-ml Dowex 50W-X8-H column and eluted with 0.1 mol/L HCl. All results were adjusted to the same protein concentration, determined with the Bradford protein assay.16 Enzyme activity was expressed as picomoles of uric acid production per milligram of protein per minute. [14C] Xanthine was completely adsorbed (>99.9%) when applied to the Dowex column. Adding allopurinol (100 µmol/L) completely inhibited enzyme activity.
Statistical Analysis
Data were presented as mean ± SEM. Nonparametric analysis (Mann Whitney U test) was used to compare groups. A P value of less than 0.05 was considered significant.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
We used an antibody that specifically reacted with XDH/XO
(anti-XO) to localize expression of this holoenzyme in tissue sections
taken from the major compartments of the human placenta. These findings
are summarized in Table 3, together with
the results of additional immunolocalization experiments described
below. First, we examined XO expression by cells found in the two
populations of chorionic villi: floating villi, which float in maternal
blood, and anchoring villi, which anchor the placenta to the uterine
wall. Both villus structures have a trophoblast covering that surrounds
a stromal core, which is composed primarily of fibroblasts and fetal
vessels. No staining of control samples with anti-XO was detected until
the third trimester, when relatively weak immunoreactivity was found in
association with syncytiotrophoblasts (Figure 1, B and D)
. In addition, weak staining
of the other cell types resident in the villi was usually observed.
When the pregnancy was complicated by preeclampsia, antibody reactivity
dramatically increased. In addition to strong staining of the
trophoblast layers, blood vessels of the stromal cores were clearly
demarcated, a particularly striking feature of this staining pattern
(Figure 1F)
.
|
. In sharp contrast, when
the pregnancy was complicated by preeclampsia, invasive
cytotrophoblasts were strongly immunoreactive with anti-XO (Figure 2H)
.
|
We compared XDH/XO holoenzyme and specific XO enzyme activity in
placental villi and placental bed curettings from preeclamptic and
control pregnancies. No difference in XDH/XO activity was detected
between the villous samples from the preeclamptic
(n = 16) and normal (n =
17) groups (5.7 ± 1.4 versus 8.5 ± 1.4 pmol/mg
protein per minute; P = 0.12). Likewise, XO isoform
activity was also not significantly different (3.1 ± 1.0
versus 4.2 ± 0.7 pmol/mg protein per minute;
P = 0.14). As shown in Figure 3
, however, the XDH/XO activity in
placental bed curettings was significantly higher in biopsies from 10
preeclamptic samples compared with control samples obtained from 12
control pregnant women (3.6 ± 0.8 versus 1.6 ±
0.4 pmol/mg protein per minute; P < 0.035). XO
activity was similarly increased (1.4 ± 0.5 versus
0.5 ± 0.1 pmol/mg protein per minute; P < 0.007;
Figure 3
). The activity ratio, XO/(XDH + XO), was not different in the
two groups (42% ± 5% versus 35% ± 3%;
P = 0.35). Although the gestational age of the
preeclamptic women sampled (33.0 ± 5 weeks) was significantly
less (P < 0.01) than that of controls
(39.6 ± 1.2 weeks), there was no evident effect of gestational
age on XDH/XO or XO activity in the preeclamptic or control women
(P = 0.15; r2
= 0.1).
|
We also investigated which cells among those of the placenta
proper or found at the maternal-fetal interface expressed two major
intracellular antioxidant enzymes—the cytosolic form of SOD
(Cu,Zn-SOD), which inactivates superoxide, and catalase, which
inactivates hydrogen peroxide. The results are summarized in Table 3.
Immunostaining for SOD was detected exclusively in association with the
various trophoblast subpopulations. In first-trimester samples, only
cytotrophoblasts of floating villi were stained (data not shown). From
the second trimester onward, all of the trophoblast populations
expressed SOD to various degrees. By the end of pregnancy, staining of
the syncytiotrophoblasts (data not shown) and invasive cytotrophoblasts
within the uterine wall was the strongest (Figure 4
; cf B, D, and F). When the pregnancy
was complicated by preeclampsia, SOD expression by the trophoblast
components of floating and anchoring villi was unaffected (data not
shown), but invasive cytotrophoblasts reacted only weakly, if at all,
with anti-SOD (Figure 4H)
.
|
The Effects of Preeclampsia on Nitrotyrosine Generation by Cells of Floating and Anchoring Placental Villi
The placenta is capable of generating NOs,17
which
can in turn react with superoxide to form peroxynitrite anions
(ONOO-) that covalently modify proteins by
nitration of tyrosine residues.18
Accordingly, we also
used immunolocalization techniques to determine whether the apparent
preeclampsia-associated changes in invasive cytotrophoblast XDH/XO
staining and XO activity were accompanied by changes in the oxidative
status of the tissue. The results are summarized in Table 3. For
control floating villi, nitrotyrosine expression was not observed in
the first (data not shown) or second trimester of pregnancy (Figure 5B)
. At term, weak staining was detected
in association with stromal cells of the villus core (data not shown).
For control invasive cytotrophoblasts, no staining was observed until
the second trimester, when a few cells reacted weakly with
anti-nitrotyrosine (Figure 5D)
. By term, faint immunoreactivity was
observed in association with most cytotrophoblasts within the uterine
wall (data not shown).
|
. Likewise, the staining intensity of invasive
cytotrophoblasts also increased (Figure 5H)
. The latter two aspects of
the expression pattern resembled the effects of preeclampsia on
staining to detect XDH/XO expression. |
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Our data demonstrate XDH/XO immunostaining in syncytiotrophoblasts of normal pregnant women. We previously reported that XDH/XO enzyme activity and messenger RNA (mRNA) are present in the placenta (although at low levels),11 contradicting older findings.10 We now find that in normal pregnancy much of this activity is localized to the syncytiotrophoblasts. Although immunostaining intensity was greater in syncytiotrophoblasts from preeclamptic, compared with normally pregnant, women, XDH/XO enzyme activity levels were not different. There was markedly greater holoenzyme immunostaining in the invasive cytotrophoblasts from preeclamptic women as compared with controls. Additionally, placental site curettings from preeclamptic women (which contain this cytotrophoblast population) had increased holoenzyme and increased XO isoform activity as compared with samples from normal women. We did not demonstrate an increased proportion of the enzyme present as XO (ratio change), which has been reported in response to hypoxia and cytokines in other systems. Although mean XO/(XDH + XO) activity ratios were greater in samples from women with preeclampsia, the differences did not achieve statistical significance perhaps due to lack of power with a small number of samples. Increased XO activity was associated with an increase in staining for nitrotyrosine associated with these cells, suggesting in vivo interaction of superoxide and NO. We have no data regarding the dynamic range of activity levels that give rise to immunofluorescence signals in the tissue localization studies. However, it should be noted that the two assays point to the same conclusion, namely, that XO expression/activity, which is normally very low, is substantially elevated at the maternal-fetal interface in preeclampsia.
We sought to determine whether the increase in superoxide indicated by these findings was associated with modifications of degradatory enzymes for superoxide. SOD converts superoxide to hydrogen peroxide, whereas catalase converts the product of that reaction, hydrogen peroxide, to water and molecular oxygen. We found no difference in catalase immunostaining within the placenta. CuZn-SOD immunostaining, however, was reduced in trophoblast cells from preeclamptic women. This is consistent with previous data measuring placental and erythrocyte CuZn-SOD activity in these patients.21-25
We note that there are several other potential enzymatic sources of
superoxide in addition to XO and other isoforms of SOD (manganese SOD
and extracellular SOD). These have different tissue and cellular
localizations that could potentially explain our overall findings.
Nevertheless, a scenario in which shallow implantation results in
reduced oxygen delivery with subsequent down-regulation of SOD and
up-regulation of XDH/XO would be compatible with our findings. In other
settings, hypoxia is a potent stimulus that increases XDH/XO
expression. Alternatively, the effect of hypoxia might not be direct,
but mediated by cytokines such as tumor necrosis factor-
(TNF-).
TNF- is known to increase XDH/XO26
and is increased in
conditioned media from cytotrophoblast and villous explants cultured
under hypoxic conditions in vitro.27
There is
also a report of increased TNF- production by preeclamptic
placentas.28
If hypoxia is a stimulus, then it is perhaps
not surprising that invasive cytotrophoblast, with oxygenation
determined by nonanastamosing basal arteries and diffusion through
several cell layers of decidua, would be affected whereas villous
cytotrophoblast exposed to extensively comingled intervillous blood
flow would not. Our findings of changes in the basal plate/placental
bed suggest that oxidative stress is more pronounced at sites where
maternal and fetal tissues intermingle, as distinct from changes in
purely fetal tissue (the villous placenta). Studies of villous explants
and isolated cytotrophoblast maintained under standard and hypoxic
culture conditions should prove useful in determining the influence of
hypoxia on XDH/XO and SOD expression.
Under appropriate stoichiometric conditions, NO will interact with superoxide to form the reactive oxygen species peroxynitrite.18 Peroxynitrite causes nitration of tyrosine residues on proteins to form nitrotyrosine.29 This has been used as a marker of in vivo activity of peroxynitrite and, for example, is found in the intima of vessels with atherosclerotic lesions.30 Myatt and coworkers have reported increased nitrotyrosine immunostaining, particularly in villous vascular endothelium, in preeclampsia.31 It is known that trophoblast can produce NO.32 Thus, the finding of nitrotyrosine residues in the invasive cytotrophoblast may reflect increased production of superoxide in this setting. Recently, however, pathways independent of superoxide have been reported for the nitration of tyrosine, such as interaction of nitrogen dioxide (NO2) with tyrosyl radicals generated by myeloperoxidase during oxidative stress.33 Thus, nitrotyrosine detection more broadly provides evidence for damage by reactive nitrogen species and, although explainable by the interaction of superoxide with NO as the pathway for formation, does not necessarily imply an increase in this interaction. There are obvious limitations of immunostaining as a quantitative technique. However, the results we obtained for XDH/XO and SOD in invasive cytotrophoblasts and for nitrotyrosine in fetal blood vessels within the villous core fall into the category of dramatic differences that were largely "all or none" and devoid of nonspecific staining.
The relationship of available concentrations of superoxide and NO with SOD is critical to determining whether NO will out-compete SOD for superoxide and thus form peroxynitrite.18 In this regard, we did not find evidence of CuZn-SOD immunostaining in fetal vessels. Our data are also compatible with altered stoichiometry of superoxide, NO, and SOD in fetal placental vessels compared with vessels in similar sites from normal infants. There are reports that the NO metabolites, nitrite and nitrate, are increased in the cord blood of infants of preeclamptic women.34 In addition, we reported that exposure of endothelial cells to plasma from cord blood of infants of preeclamptic mothers increases NO production.35
These data provide overall support for a local increase in reactive oxygen species generation in the placental beds of preeclamptic women. Whether this could lead to oxidative stress systemically is uncertain. The activity of XO in placental site curettings was greater, but the activity of XO in villous trophoblast was similar in samples from both preeclamptic and control women. The activity of the enzyme was, in general, greater in villous trophoblast than in placental site curettings, and there is much more villous than invasive trophoblast tissue. However, despite similar XO activity of villous trophoblast, the fetal vessels inside the villi of preeclampsia placentas manifest increased nitrotyrosine labeling, which might arise from increased exposure to superoxide. Could there be systemic effects from the elevated placental XO in the invasive cytotrophoblast of preeclamptic women? It is possible that the relatively small amount of enzyme in invasive cytotrophoblast could result in greater production of superoxide (and peroxynitrite) than in the villous trophoblast, if the stoichiometry of NO, superoxide, and SOD was appropriate. It could also be possible that, in the decidual environment, a relative paucity of antioxidants or presence of other seeding-reactive oxygen species might favor propagation of oxidative damage. Further support for linkage between XO, superoxide production, and oxidative damage will ultimately require measurement of control and preeclamptic placental tissue superoxide production and the impact of inhibitors of XO. In this regard, it is noteworthy that a recent reappraisal of XO in human tissues has suggested that both XDH and XO isoforms can generate reactive oxygen species during posthypoxic reperfusion.36
In summary, we have demonstrated increased activity of XO, a free-radical–generating enzyme, in invasive cytotrophoblast from preeclamptic women. This activity is accompanied by a reduction of SOD expression and increased nitrotyrosine labeling, suggestive of local peroxynitrite generation. The mechanisms explaining the XO increase, and the implications of this local increase to generalized oxidative stress remain to be determined.
|
Acknowledgements |
|---|
|
Footnotes |
|---|
Supported by National Institutes of Health grant PO1 HD30367 and the Irene McClenahan Young Investigator Award Fund of Magee Women’s Health Foundation.
Accepted for publication September 4, 1999.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
concentrations and mRNA expression are increased in preeclamptic placentas. J Reprod Immunol 1996, 32:157-169[Medline]
This article has been cited by other articles:
 |
|
 |
|
  I. Craici, S. Wagner, and V. D. Garovic Review: Preeclampsia and future cardiovascular risk: formal risk factor or failed stress test? Therapeutic Advances in Cardiovascular Disease, August 1, 2008; 2(4): 249 - 259. [Abstract] [PDF]
|
|
|
|
|
|
P. Lopez-Jaramillo, W. D. Arenas, R. G. Garcia, M. Y. Rincon, and M. Lopez Review: The role of the L-arginine-nitric oxide pathway in preeclampsia Therapeutic Advances in Cardiovascular Disease, August 1, 2008; 2(4): 261 - 275. [Abstract] [PDF]
|
|
|
|
 |
|
 R. E. Gandley, J. Rohland, Y. Zhou, E. Shibata, G. F. Harger, A. Rajakumar, V. E. Kagan, N. Markovic, and C. A. Hubel Increased Myeloperoxidase in the Placenta and Circulation of Women With Preeclampsia Hypertension, August 1, 2008; 52(2): 387 - 393. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Jauniaux, L. Poston, and G. J. Burton Placental-related diseases of pregnancy: involvement of oxidative stress and implications in human evolution Hum. Reprod. Update, November 1, 2006; 12(6): 747 - 755. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Nash, M. Olovsson, and U. J. Eriksson Placental Dysfunction in Suramin-Treated Rats: Impact of Maternal Diabetes and Effects of Antioxidative Treatment Reproductive Sciences, April 1, 2005; 12(3): 174 - 184. [Abstract] [PDF]
|
|
|
|
 |
|
 D. M. Shah Role of the renin-angiotensin system in the pathogenesis of preeclampsia Am J Physiol Renal Physiol, April 1, 2005; 288(4): F614 - F625. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Banerjee, A. Smallwood, J. Moorhead, A. E. Chambers, A. Papageorghiou, S. Campbell, and K. Nicolaides Placental Expression of Interferon-{gamma} (IFN-{gamma}) and Its Receptor IFN-{gamma}R2 Fail to Switch from Early Hypoxic to Late Normotensive Development in Preeclampsia J. Clin. Endocrinol. Metab., February 1, 2005; 90(2): 944 - 952. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. T. M. Raijmakers, R. Dechend, and L. Poston Oxidative Stress and Preeclampsia: Rationale for Antioxidant Clinical Trials Hypertension, October 1, 2004; 44(4): 374 - 380. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. A. Hubel, L. M. Bodnar, A. Many, G. Harger, R. B. Ness, and J. M. Roberts Nonglycosylated Ferritin Predominates in the Circulation of Women with Preeclampsia but Not Intrauterine Growth Restriction Clin. Chem., May 1, 2004; 50(5): 948 - 951. [Full Text] [PDF]
|
|
|
|
 |
|
 G. K. Kumar and J. B. Klein Analysis of expression and posttranslational modification of proteins during hypoxia J Appl Physiol, March 1, 2004; 96(3): 1178 - 1186. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T.-H. Hung, D. S. Charnock-Jones, J. N. Skepper, and G. J. Burton Secretion of Tumor Necrosis Factor-{alpha} from Human Placental Tissues Induced by Hypoxia-Reoxygenation Causes Endothelial Cell Activation in Vitro: A Potential Mediator of the Inflammatory Response in Preeclampsia Am. J. Pathol., March 1, 2004; 164(3): 1049 - 1061. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Noris, M. Todeschini, P. Cassis, F. Pasta, A. Cappellini, S. Bonazzola, D. Macconi, R. Maucci, F. Porrati, A. Benigni, et al. L-Arginine Depletion in Preeclampsia Orients Nitric Oxide Synthase Toward Oxidant Species Hypertension, March 1, 2004; 43(3): 614 - 622. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Bauer, J. Pollheimer, J. Hartmann, P. Husslein, J. D. Aplin, and M. Knofler Tumor Necrosis Factor-{alpha} Inhibits Trophoblast Migration through Elevation of Plasminogen Activator Inhibitor-1 in First-Trimester Villous Explant Cultures J. Clin. Endocrinol. Metab., February 1, 2004; 89(2): 812 - 822. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Dechend, C. Viedt, D. N. Muller, B. Ugele, R. P. Brandes, G. Wallukat, J.-K. Park, J. Janke, P. Barta, J. Theuer, et al. AT1 Receptor Agonistic Antibodies From Preeclamptic Patients Stimulate NADPH Oxidase Circulation, April 1, 2003; 107(12): 1632 - 1639. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Roberts, G. Pearson, J. Cutler, and M. Lindheimer Summary of the NHLBI Working Group on Research on Hypertension During Pregnancy Hypertension, March 1, 2003; 41(3): 437 - 445. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T.-H. Hung, J. N. Skepper, D. S. Charnock-Jones, and G. J. Burton Hypoxia-Reoxygenation: A Potent Inducer of Apoptotic Changes in the Human Placenta and Possible Etiological Factor in Preeclampsia Circ. Res., June 28, 2002; 90(12): 1274 - 1281. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T.-H. Hung, J. N. Skepper, and G. J. Burton In Vitro Ischemia-Reperfusion Injury in Term Human Placenta as a Model for Oxidative Stress in Pathological Pregnancies Am. J. Pathol., September 1, 2001; 159(3): 1031 - 1043. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Black, H. Yu, J. Lee, M. Sachchithananthan, and R. L. Medcalf Physiologic Concentrations of Magnesium and Placental Apoptosis: Prevention by Antioxidants Obstet. Gynecol., August 1, 2001; 98(2): 319 - 324. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
