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Biomedical subjects

L Mazzanti

Publications and source records attributed to L Mazzanti.

At least 91 records · Page 5Linked to original sources
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

Effect of divalent cations on Na+,K(+)-ATPase obtained from human placenta.

Circular dichroism (CD) and acrylamide quenching studies of Na+,K(+)-ATPase from human placenta showed that its incorporation into phosphatidylcholine vesicles increased the enzymic activity by 55%. Moreover, both with the purified and the vesicle-reconstituted protein, Ca2+ and Mg2+ increased the activity, the effect being more pronounced after preincubation of the protein with Mg2+. CD data suggest that this activity increase may be linked to a change in the secondary structure of the ATPase, in particular beta-turn, beta-sheet and random coil. Acrylamide quenching studies suggest that ions could primarily interact with phospholipid head groups, but not directly with the protein.

Calcium↗
PubMed1993

Effect of hydroxymethylglutaryl-CoA reductase inhibitors on the functional properties of erythrocyte membranes.

We studied 56 patients affected by primary hypercholesterolemia treated with placebo for 1 month and with simvastatin (20 mg/day) or pravastatin (20 mg/day) for 6 months during a double-blind clinical trial. At 1-month intervals we determined the following parameters in the serum: total and HDL cholesterol, triglycerides, and apolipoprotein A-1 and B. At the same time intervals we also determined the cholesterol and phospholipid concentration, the Na+/K+ ATPase activity, and the fluidity of erythrocyte membranes. Our results demonstrated the following modifications in the erythrocyte membranes during simvastatin and pravastatin treatments: (1) an initial increase in cholesterol concentration and in cholesterol/phospholipid molar ratio, with a significant decrease only after 4 months; (2) a similar behavior of membrane fluidity, with an initial decrease and an elevation after 4 months; (3) an increase in the Na+/K+ ATPase activity only after 4 months. We hypothesize that simvastatin and pravastatin not only inhibit the hepatic synthesis of cholesterol, but also modify the cholesterol exchange between plasma and the erythrocyte membrane.

Adolescent↗
PubMed1993

Alterations in Na+/K(+)-ATPase activity and fluidity of erythrocyte membranes from relatives of insulin dependent diabetic patients.

Several plasma membrane alterations have been described in diabetes mellitus. Data reported in gestational diabetes mellitus (GDM) suggested that these alterations might be present before the onset of overt metabolic derangement. On the basis of these data it is tempting to hypothesize that the reduction in the sodium pump activity might be due to a genetic factor acting at the membrane level before the onset of diabetes. In order to verify this hypothesis 11 insulin-dependent diabetic patients, 15 first degree relatives of the patients and 10 healthy subjects with a negative family history for diabetes mellitus were studied. Fluidity, Na+/K(+)-ATPase activity and membrane cholesterol content (C) were evaluated on plasma membranes obtained from red blood cells (RBCs). Na+/K(+)-ATPase activity was reduced with a contemporary increase in membrane fluidity in RBCs from IDDM patients in comparison to either relatives and controls. The same alterations were observed also in RBCs from the relatives in comparison to controls. We did not find any significant difference in the C content among the three groups. Data herein reported provide evidence that a reduction in the Na+/K(+)-ATPase activity is present in the plasma membrane of relatives of diabetic subjects. Furthermore, the present work suggests that the change in enzymatic activity might be related to modifications in membrane fluidity.

Adolescent↗
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

Diabetes mellitus induces red blood cell plasma membrane alterations possibly affecting the aging process.

Various alterations of red blood cell (RBC) plasma membrane appear both in diabetes mellitus and during the physiological aging process. Diabetes mellitus decreases RBC life-span; therefore, it may change the plasma membrane by acting through its effect on the aging process. In order to clarify the issue, RBCs from normal subjects and insulin-dependent diabetic patients were fractionated in five subpopulations of different mean age (fraction 1: early young RBC, fraction 5: mature RBC). Thereafter, plasma membranes were prepared and enzymatic activities, membrane fluidity and lipid peroxidation were evaluated. NA+, K(+)-ATPase activity decreased during aging and it was higher in all RBC subpopulations from normal subjects in comparison to diabetic patients. Next, lipid peroxidation and fluidity increased during aging in both the study groups; in this case, however, in all subpopulations, except for that from fraction 1, RBCs from diabetic patients showed higher membrane fluidity and lipid peroxidation in comparison to normal subjects. Data herein reported suggest that diabetes mellitus affects the plasma membrane independently of (lipid peroxidation and fluidity) or dependently on (Na+, K(+)-ATPase) its effect on aging. In the case of lipid peroxidation and fluidity diabetes mellitus seems to affect the membrane by decreasing RBC life span, whereas in the case of Na+K(+)-ATPase it seems to alter this enzymatic activity which in turn might affect RBC aging. Acetylcholinesterase activity decreased during aging in RBCs from normal subjects, but it increased in RBCs from diabetic patients; RBC subpopulation from fraction 1, on the other hand, showed similar values in normal subjects and diabetic patients. In this case the effect of diabetes mellitus appears only during aging.

Acetylcholinesterase↗
PubMed1992

Magnesium pyrrolidone carboxylate infusion reduces angiotensin II pressor response in pregnant women at risk for hypertension.

OBJECTIVE: Our objective was to investigate the possible restoring action of magnesium on vascular sensitivity to angiotensin II in pregnancy. STUDY DESIGN: We studied intraplatelet free calcium and the pressor response to angiotensin II in 10 primigravid women (28 to 32 weeks' gestation) at risk for pregnancy induced hypertension on the basis of altered uteroplacental blood velocity waveforms at 20 weeks' gestation, before and after the infusion of 1 gm of magnesium pyrrolidone carboxylate. After the effective pressor dose was achieved or a maximum of 32 ng/kg per minute was reached, we infused 1 gm magnesium pyrrolidone carboxylate and repeated the test. Intraplatelet free calcium was measured by means of fluorescent probes at the beginning and the end of both tests. RESULTS: Six women were classified as refractory to angiotensin II and four as sensitive (effective pressor dose < 10 ng/kg per minute). After magnesium pyrrolidone carboxylate infusion, the four sensitive women became refractory and the effective pressor dose was significantly enhanced to 32 in all six refractory women. Intracellular free calcium increased significantly during the first angiotensin II infusion, whereas after magnesium pyrrolidone carboxylate administration it did not change significantly. CONCLUSIONS: Magnesium pyrrolidone carboxylate enhances the vascular refractoriness and intracellular free calcium mediates the pressor response to angiotensin II in pregnancy.

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↗
PubMed1992

Effects of calcium on Na+,K(+)-ATPase isolated from human placenta.

It has been reported that Ca2+ can be either stimulatory or inhibitory of the activity of Na+,K(+)-ATPase obtained from different sources. The aim of the present work was to study the effect of increasing concentrations of Ca2+ on Na+,K(+)-ATPase activity and of placenta. The temperature dependence of Na+,K(+)-ATPase activity and of spectral parameters of a spin label paramagnetic maleimide) were also (MSL, 2,2,6,6-tetramethylpiperidin-1-oxyl-4-maleimide) were also investigated in absence and in presence of 2 mM Ca2+. Ca2+ affects positively the enzymatic activity and this effect is evident at all temperature tested. Maleimide spectral parameters are not affected by the presence of 2 mM Ca2+, showing that the microenvironments of SH groups are not modified following ion interactions.

Calcium↗
PubMed1992

Lifetime determination of low sample concentrations: a new cuvette for highly accurate and sensitive fluorescence measurements.

A new cuvette was developed for spectrofluorometric measurements which increases the efficiency of recorded fluorescence emission by at least two-fold, decreasing, at the same time, the noise component of the record. It is suited for both steady-state and dynamic fluorescence measurements. Comparative data for both the classical and the novel cuvettes are presented here.

Data Interpretation, Statistical↗
PubMed1991

Reliability assessment of a gas chromatographic method for polycyclic aromatic hydrocarbons in olive oil.

A quality control test was developed for a gas chromatographic method to determine polycyclic aromatic hydrocarbons in olive oil. Fifteen oil specimens were fortified with eight three- to six-ring polycyclic aromatic hydrocarbons at levels of between 3.0 (approximate detection limit) and 360 micrograms/kg. Three sets of five equally fortified specimens were obtained and assayed at random by three operators. For each fortification level, the means of recovery yield were in the range 56-107%, and were independent of the polycyclic aromatic hydrocarbon congener specificity and the operator's capability. Excluding subsets of data associated with both the fortification level at the detection limit and a deviant polycyclic aromatic hydrocarbon term (benzo[ghi]perylene), an overall mean accuracy of 96% and a precision of 7% were achieved.

Chromatography, Gas↗
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↗