Biomedical subjects

N Cester

Publications and source records attributed to N Cester.

At least 37 records · Page 2Linked to original sources

PubMed1994

Pregnancy induced hypertension: a role for peroxidation in microvillus plasma membranes.

It has been recently hypothesized that in PIH a placental oxidant-antioxidant imbalance might cause the release of lipoperoxidation products into the circulation, with subsequent damage of endothelial cell membranes. In this hypothesis the endothelial cell and further increase in circulating lipoperoxide levels, which are by themselves able to induce smooth muscle constriction and increased pressor responsiveness to angiotensin II. In order to investigate this issue, we studied the basal content of lipid peroxides in terms of malondialdehyde (MDA) in the syncytiotrophoblast plasma membranes (SPM) from PIH women. Moreover, we investigated the susceptibility to peroxidation of SPM using an in vitro oxidative stress as a tool to verify the predisposition to the in vivo development of peroxidation products. The fatty acid composition of the membranes was also analyzed. Microvillus membrane lipoperoxide concentrations were significantly increased in PIH women (62.8 +/- 7.6 ng MDA/mg prot) compared with healthy pregnant subjects (37.6 +/- 4.8 ng MDA/mg prot; p < 0.01). The formation of TBARS under the action of phenylhydrazine was significantly greater in PIH women (90.3 +/- 7.4 mmol MDA/mol cholesterol) than in normal pregnant subjects (68.6 +/- 6.4 mmol MDA/mol cholesterol; p < 0.01). In PIH microvillus membrane we also observed a significant increase of the content of polyunsaturated arachidonic acid. The increased susceptibility to oxidative stress of SPMs from PIH women might be due either to reduced antioxidant systems or to an abnormality of the lipid composition of the membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Human hypertensive placenta contains an increased amount of Na,K-ATPase with higher affinity for cardiac glycosides.

Placentas of women suffering from pregnancy-induced hypertension (PIH) were found to contain a greater amount of Na,K-ATPase molecules, estimated from anthroyl ouabain binding, than normotensive individuals. Both the microsomal fraction of placental cells and purified Na,K-ATPase showed an increased affinity for the specific inhibitor ouabain which, in the case of the microsomes, bound with a dissociation constant of 0.9 nM as compared with 3.4 nM in the controls. Likewise, the dissociation constant of the ouabain complex with purified Na,K-ATPase was about 3.5 times lower in the hypertensive patients. The differences are apparently caused by a different microenvironment of the ouabain-binding site, as reflected in the quantum yield of bound anthroyl ouabain. If an endogenous digitalis-like factor is present in the body fluids to regulate Na,K-ATPase activity, the present results render its role quite plausible.

Adult↗

PubMed1994

Na,K-ATPase from placenta of women with pregnancy-induced hypertension exhibits an increased affinity for cardiac glycosides.

Microsomes were prepared from placentas of normotensive women and of patients suffering from pregnancy-induced hypertension (PIH). Activity of Na,K-ATPase (estimated as ATP hydrolysis) from the hypertensive tissue was lower than from tissue of normotensive women, even if the number of Na,K-ATPase molecules (monitored by anthroyl ouabain binding) was actually greater in the hypertensive tissue. The affinity of Na,K-ATPase for anthroyl ouabain was about four times higher in plasma membranes of hypertensives, indicating some structural change in the Na,K-ATPase or in its vicinity. Assuming the presence of an endogenous digitalis-like factor, the results suggest a simple way of explaining not only the lower Na,K-ATPase activity in the placental membranes of hypertensives but also the different extent of enzyme inhibition in different tissues of PIH patients.

Anthracenes↗

PubMed1993

Cultured human trophoblast cells reproduce the initial events of placental biology.

OBJECTIVE: The objective of this study was to determine whether cultured trophoblast cells shared the same morphological and biological properties observed in trophoblast, in vivo. STUDY DESIGN: Trophoblast cells from human term placenta were cultured, morphologically, biochemically and immunochemically monitored for as long as 30 days. RESULTS: Single cells progressively aggregated and fused into a syncytio, the Ca2+ and the Ca(2+)-ATPase activity drooped, and the 72 kDa collagenase (MMP-2) was consistently expressed. CONCLUSIONS: Term placenta trophoblast cultures can be viewed and used as a model system mimicking morphological and biochemical events of placenta biology and differentiation.

Calcium↗

PubMed1993

Altered lipid composition, increased lipid peroxidation, and altered fluidity of the membrane as evidence of platelet damage in preeclampsia.

OBJECTIVE: To assess lipid composition, lipid peroxidation, and fluidity of the membrane of platelets from preeclamptic women. METHODS: We studied 40 primigravid women at 28-32 weeks' gestation; 20 were preeclamptic and 20 were normotensive. After preparing platelet membranes, we extracted lipids, measured cholesterol and phospholipid concentrations, and calculated the proportion of unsaturated to saturated fatty acids. Lipid peroxides expressed as conjugated dienes were determined by spectrophotometry. Membrane fluidity was determined by means of fluorescent lipophilic probes. Statistical analysis was performed by the Student t test, with significance at P < .05. RESULTS: Cholesterol concentration, cholesterol-to-phospholipid ratio, the amount of unsaturated fatty acids, conjugated dienes, and membrane fluidity significantly increased in platelets from preeclamptic patients as compared with the normotensive women. CONCLUSIONS: The discrepancy between cholesterol increase and membrane fluidity increase is consistent with the increase in unsaturated fatty acid content. In the platelet membrane, unsaturated fatty acids constitute the larger substrate for lipid oxidation and can also take part in the formation of thromboxane. Therefore, platelet membrane damage in preeclampsia, through imbalance of thromboxane A2/prostacyclin production, may contribute to the onset or maintenance of vasoconstriction and hypertension.

Adult↗

PubMed1993

Local anaesthetic effects on trophoblast membrane fluidity.

Previous studies showed that anaesthesia with the barbiturate Thiopental induces an increase in membrane fluidity and a decrease in acetylcholinesterase activity in syncytiotrophoblast plasma membranes (SPM) obtained from placentas after Cesarean section. The aim of the present work was to compare the effect of a local anaesthetic (bupivacaine hydrochloride, trade name Marcaine) on SPM in vivo and to establish whether the anaesthetic is still present in the membrane after tissue preparation. The acetylcholinesterase activity was lower in Marcaine-anaesthetized SPM (27 +/- 3 against 39 +/- 6 in the control). The Marcaine action on the SPM can be ascribed to a competitive inhibition, similar to that reported for Thiopental. Fluorescence studies of the order parameter P showed it to be higher in SPM obtained from control (0.253 +/- 0.012) than in SPM obtained from Marcaine-exposed membranes (0.240 +/- 0.015). The local anaesthetic is still present in the SPM after their preparation (20.1 ng per mg membrane protein). It appears that the local anaesthetic exhibits an effect similar to that of the general anaesthetic, apparently due to binding to the membrane.

Acetylcholinesterase↗

PubMed1992

Changes in membrane fluidity and Na+/K(+)-ATPase activity during human trophoblast cell culture.

The human placenta plays an essential role in embryo development, in particular regulating the transport of ions, nutrients and immunoglobulins from the maternal to the fetal circulation. Trophoblast organization into a syncytial layer involves structural and functional steps that may be monitored and elucidated by in vitro studies. The structural stages by which the syncytial trophoblast is formed are not yet understood. In order to clarify the mechanism of trophoblast development, we studied the morphological characteristics of the syncytial trophoblast formation in culture and the functional changes (transport properties and membrane microviscosity) accompanying the structural modifications. By using both 5-nitroxystearate and 16-nitroxystearate as spin labels, we observed an initial increase in membrane order over 0-24 h of culture, which can be associated with two events: recovery of cell membranes from trypsin and initial aggregation of cytotrophoblasts. The similar behaviour of the order parameters determined with both probes indicates that membrane order changes both inside and in the outer part of the lipid bilayer. The subsequent decrease in membrane order observed at 36-48 h might be related to the process of cellular fusion. The increase in sodium/potassium pump activity in the first 24 h of culture might be an expression of cell recovery following trypsin treatment. The subsequent decrease might represent an adaptive mechanism by which metabolic energy is mainly used for morphogenetic changes.

Cells, Cultured↗

PubMed1992

Modifications in platelet membrane transport functions in insulin-dependent diabetes mellitus and in gestational diabetes.

The pathogenesis of plasma membrane alterations present in diabetes mellitus is unclear. To add new insights to the question, platelet membrane properties were evaluated in 16 women presenting impaired glucose tolerance at the 28-29th week of gestation (GDM) and in 8 women with insulin-dependent diabetes mellitus (IDDM). 15 healthy pregnant women (HPW) and 21 healthy non-pregnant (HNPW) women were the control group for GDM and IDDM, respectively. Pregnancy (HPW vs. HNPW) provoked an increase in Ca(2+)-ATPase activity and a decrease in membrane fluidity; in contrast, Na+/K(+)-ATPase, intracellular free Ca2+ concentrations, membrane cholesterol and phospholipid content did not vary. Both GDM and IDDM showed lower Na+/K(+)-ATPase activity and higher Ca2+ concentration, compared to HPW and HNPW, respectively, whereas Ca(2+)-ATPase activity was higher only in IDDM; furthermore, membrane fluidity was lower in GDM and higher in IDDM. Finally, GDM showed higher membrane cholesterol content. Both GDM and IDDM showed a very good metabolic control so that variations reported cannot be due to hyperglycemia; it is tempting to suggest that membrane variations are present before the clinical metabolic alteration. Furthermore, both GDM and IDDM were on insulin therapy, therefore: (i) insulin may be the pathogenetic factor of higher intracellular free Ca2+ concentrations and lower Na+/K(+)-ATPase activity since they both varied accordingly in GDM and IDDM, but not of (ii) changes in Ca(2+)-ATPase, membrane fluidity and cholesterol content which did not vary accordingly in GDM and IDDM.

Adult↗

PubMed1992

Placental villi-decidua interactions in normal and hypertensive pregnancies: a morphological quantitative study.

The decidual response to the implantation of the embryo is characterized by physical modifications to the uterine wall, with proliferation of the stromal cells which later change into decidual cells. We performed associated morphological and morphometrical studies to assess how the placental villi and decidua intersect, both in normal terminal pregnancy and in hypertensive patients in whom microenvironmental modifications induced by hypertension may cause significant alterations in mother-fetus relationships. In placentas of hypertensive women our morphometric analyses showed a higher number of chorionic villi-decidua interactions (p less than 0.05) with a more clumped distribution (p less than 0.05) and a smaller surface area of single interaction (p less than 0.001), in association with a higher number (p less than 0.005), and greater areas (p less than 0.01) of decidual cells. These data demonstrate how the placenta can enhance mother-fetus contacts impaired as the result of a hypertensive condition.

Chorionic Villi↗

PubMed1991

Modifications induced by gestational hypertension on platelet calcium transport.

Several studies have recently demonstrated that the platelets of subjects affected by essential hypertension have, in their basal state, an elevated cellular calcium content. Such data appear particularly interesting with regard to gestational hypertension (GH). Supposing that the intracellular calcium may be involved in the regulation of blood pressure we have studied the cytosolic calcium concentration, Na+/K(+)-ATPase activity, Ca(2+)-ATPase activity, fluidity, and the cholesterol/phospholipid (C/P) molar ratio of the plasma membranes in platelets from 20 normotensive pregnant women and 20 women affected by mild gestational hypertension without pharmacological treatment, near term. We observed an increased Ca(2+)-ATPase activity and a decreased Na(+)K(+)-ATPase activity in GH compared to the controls, accompanied by an increased Ca2+ intraplatelet concentration in the same patients. The fluidity and the C/P molar ratio were also increased. Our study gives indirect support to the hypothesis, supposing a reduced Na+/K(+)-ATPase activity which might cause increased intracellular Na+ content and decreased Ca2+ efflux through the Na+/Ca2+ exchange. However, out data can not rule out the other hypotheses explaining the increased cellular Ca2+ content. The present data indicate that GH is accompanied by a membrane structural abnormality that alters its physical state and modifies the membrane-related cellular functions.

Biological Transport, Active↗

PubMed1991

Modifications induced by gestational diabetes mellitus on cellular membrane properties.

Alterations in erythrocyte plasma membrane properties (enzymatic activities and membrane fluidity) have been observed in patients affected by insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). In order to verify whether these alterations are present also in gestational diabetes mellitus (GDM) we studied the plasma membranes obtained from two different cellular types (erythrocyte from both mother and cord blood and placenta syncytiothrophoblast cell) of 16 healthy pregnant women and 15 women affected by GDM. The following determinations were performed on the membrane preparations: Na+/K(+)-ATPase activity, acetyl-cholinesterase (AchE) activity, membrane fluidity and cholesterol:phospholipid ratio. We observed a reduction of both enzymatic activities and a decrease of membrane fluidity in maternal and cord blood erythrocytes and in syncytiotrophoblast plasma membranes in GDM pregnant women in comparison with controls. The cholesterol to phospholipid ratio was significantly lower in the erythrocyte membranes of women affected by GDM than in normal pregnant women, while it was increased in the cord blood erythrocyte membranes and in placental membranes in GDM in comparison with controls. The present study found, in GDM patients, a membrane alteration similar to the abnormality reported in IDDM and NIDDM (i.e. decreased Na+/K(+)-ATPase activity), while opposite modifications were observed with regard to other membrane activities and properties. The different membrane alterations observed in GDM with respect to IDDM and NIDDM might be linked to the different degree of metabolic control, on the contrary the reduced Na+/K(+)-ATPase activity might be a primary event in the pathogenesis of diabetes mellitus per se and might constitute a signal of high risk of developing the disease later in the women affected by GDM during pregnancy.

Acetylcholinesterase↗

PubMed1991

In vitro effect of magnesium on the Na/K-ATPase isolated from human placenta.

Magnesium (Mg) is an activator of many cellular processes, among which is cation transport. An imbalance of cation transport may be involved in several diseases, as well as during pregnancy. Since the action of Mg in vivo in preventing gestational diseases is known, as well as its role in vitro on some cation transport activities, we studied the action of increasing concentrations of Mg on the activity of the enzyme Na/K-ATPase isolated from placental tissue of six normotensive women, at term. Incubation in a medium with increasing concentrations of Mg resulted in a significant activation of the enzyme, which was related to Mg concentration. The study demonstrates the action of Mg in vitro on isolated enzymes, and suggests the use of enzyme purification as a model for the study of cation transport in pregnancy.

Dose-Response Relationship, Drug↗

PubMed1991

Effect of magnesium-deficient diet on cation transport in pregnant rabbits.

The imbalance of cation transport is considered to play an important role in the development of hypertension, and this also applies to hypertension during pregnancy. Magnesium (Mg) is one of the factors that regulate cation transport across the cell membrane. We therefore studied the effect of a magnesium-deficient diet on the activity of erythrocyte Na/K-ATPase and Mg-ATPase from six pregnant rabbits and compared the results to those obtained from six controls on a normal diet. None of the rabbits on the deficient diet developed hypertension or intrauterine growth retardation; nevertheless the activity of both enzymes was significantly reduced compared to the group on the normal diet. Since the reduced activity of these enzymes can determine sodium or calcium retention in the cell, Mg deficiency could be the basis of the onset of some forms of hypertension in pregnancy.

Animals↗

PubMed1990

Modifications induced by general anesthetics on Na+/K+ ATPase obtained from human placenta.

Previously it was demonstrated that thiopental in vivo anesthesia didn't affect the Na+/K(+)-ATPase activity of syncythiotrophoblast plasma membrane, while affecting other enzymatic activity. The aim of the present work was to investigate if this lack of effect of thiopental on the Na+/K+ ATPase activity might be due to its specificity of action on definite membrane proteins or if the binding sites of the anesthetic to this enzyme might be masked within the membrane. Temperature dependence of the Na+/K(+)-ATPase activity and of a spin label paramagnetic maleimide derivative (MSL,2,2,6,6-tetramethylpiperidin-1-oxyl-4-maleimide), which shows a selective binding to the reduced sulfhydryl groups of proteins were investigated. This report shows that a Na+/K(+)-ATPase membranous preparation obtained from placental tissue is strongly inhibited by thiopental.

Anesthetics↗

PubMed1990

[In vitro structural aspects of the human trophoblastic cell].

Maternal- fetal exchanges are mainly regulated by trophoblast, which displays an active role during embryo growth. Trophoblast organization into a syncytial layer involves structural and functional steps that may be monitored and better elucidated by "in vitro" studies. In light of this, we have carried out morphological and biochemical analyses in order to evaluate 1) the syncytiotrophoblast formation in culture (48 h, 5-30 days) the Na+/K+ATPase activity and 3) the plasmalemmal microviscosity changes occurring during "in vitro" trophoblast production. Morphological and biochemical modulations have been pointed out.

Cells, Cultured↗

PubMed1989

Calcium and sodium transport in gestational hypertension.

The enzymatic activities of Na+/K+ ATPase and Ca2+ ATPase were determined on erythrocyte membranes from 9 normotensive and 9 gestational hypertensive pregnant women near term. A reduction in the activity of the Na+/K+ ATPase and a relative increase in the activity of the Ca2+ ATPase were found in the hypertensive patients, possibly due to a conformational alteration of erythrocyte membranes. This observation supports the possible role of the transmembrane cation transport in the pathogenesis of gestational hypertension.

Adult↗

PubMed1989

Morphological development of the human placenta in normal and complicated gestation: a quantitative and ultrastructural study.

In order to evaluate the structural potentialities of the placenta, we analyzed placentas in the following conditions: normal full term gestation, hypertensive status, twin pregnancy and abortion at 8-12 weeks of gestation, comparing cell structures, surface organization and tissue reaction. We quantitatively evaluated (1) the arborization of the placental villous tree, and (2) the microvillous density per unit of surface area, paralleling these data with ultrastructural and immunohistochemical features. In early gestation (8-12 weeks of pregnancy) the limited degree of branching of placental villi parallels a reduced number of clefts per unit of surface area (0.7/1,000 microns2), if compared with controls (2.7/1,000 microns2). In the full term twin placenta, the number of furrows is 2.26/1,000 microns2: this value reflects a low arborization potentiality, testifying to a low placental maturity. On the contrary, a high branching of the placental villous tree is present at term in hypertension. In this gestational condition, the number of sulci of 3.1/1,000 microns2 reveals a compensatory attitude of the placenta, aiming to sustain the impaired fetal-maternal metabolic interchange. In all these cases, syncytiotrophoblastic microvilli are reduced in number in comparison with the normal placenta, and this is likely to be an expression of a low trophoblastic maturation degree. The placenta is a barrier with a highly specialized function that conditions fetal outgrowth, and microenvironmental modifications are promptly faced by this structure through morphofunctional modulations.

Female↗

PubMed1989

[Hypertension and syncytiotrophoblast: morpho-structural aspects].

Hypertension is a pathological condition that involves maternal fetal relationship. In hypertension placenta displays a syncytiotrophoblast plasmalemma with aspects of anomalous behaviour concerning Intramembranous Particles (IMP) and actin content of microvilli cytoskeleton. Decrease of syncytiotrophoblast microvilli IMP and microvilli actin further sustain the tendency of hypertensive placenta to show some features of immaturity that might deeply influence fetal-maternal exchanges during pregnancy associated with pathological status.

Calcium↗