Search PubMed⌕ Search

Biomedical subjects

P Fievet

Publications and source records attributed to P Fievet.

At least 19 recordsLinked to original sources
PubMed2006

[A high troponin value: about a favourable evolution case].

Cardiac troponin I (TnIC) is a sensitive and specific marker for myocardial injuries. A part from its diagnosis character, troponin is a major element for mid term prognosis with regard to occurred cardiovascular events. We are reporting the case of a 56-year-old man admitted to hospital for an inaugural myocardial infarction with positive evolution despite a very high level of troponin (1200 ng/ml) in post re-vascularisation. The context of moderate risk factors and the early re-vascularisation probably contributed to a favourable evolution of the patient. A very high troponin value seems to be more in favour of an effective re-perfusion rather than a mid term prognosis factor in this case.

Biomarkers↗
PubMed2003

Evaluation of the "DSPM" model on a titania membrane: measurements of charged and uncharged solute retention, electrokinetic charge, pore size, and water permeability.

The DSPM (Donnan steric partitioning pore model) was evaluated in the case of a titania membrane with "nanofiltration properties" by measuring the electrokinetic charge, pore size, and water permeability of the membrane, along with charged and uncharged solute retention. The zeta potential values (zeta) were determined from measurements of the electrophoretic mobility (EM) of titania powder forming the filtering layer of the membrane. Zeta potential values were converted into membrane volume charge (X) by assuming two limiting cases: a constant surface charge (sigma(s)(cst)) and a constant surface potential (psi(s)(cst)). The mean pore radius and thickness/porosity ratio of the membrane were determined by permporometry and from water permeability measurements, respectively. Retention measurements were carried out as a function of the permeate volume flux for both neutral solutes (polyethylene glycol PEG of different size) and salts (KCl, MgSO4, K2SO4, and MgCl2) at various pH values. Ionic retentions showed minimum values near the IEP of the membrane. Retention data were analyzed using the DSPM. Very good agreement was found between the pore radius calculated by the model and that determined by permporometry. X values calculated from fitting retention data using the DSPM were also in satisfactorily agreement with X values calculated from EM measurements assuming a constant surface potential for a large pH range. Furthermore, the DSPM leads to X values (X(DSPM)) between those calculated from EM (X(EM)) using the two limiting bounds. In other words, X(DSPM) was higher than X(EM) assuming psi(s)(cst) at pH values far from the isoelectric point (IEP) and lower than X(EM) assuming sigma(s)(cst). These results show that the DSPM is in qualitative agreement with the charge regulation theory (increase of the pore surface potential and decrease of the pore surface charge density with decreasing the pore size). On the other hand, the thickness/porosity ratio of the membrane calculated from solute retention data differed significantly from that determined from water permeability measurements. Moreover, a single value of Deltax/Ak could not be determined from PEG and salt retention data. This means that the Deltax/Ak parameter loses its physical meaning and includes physical phenomena which are not taken into account by the DSPM. Nevertheless, the model satisfactorily predicted the limiting retention, as this is not influenced by the Deltax/Ak parameter.

Electrophoresis↗
PubMed2003

Contribution of convection, diffusion and migration to electrolyte transport through nanofiltration membranes.

Transport mechanisms through nanofiltration membranes are investigated in terms of contribution of convection, diffusion and migration to electrolyte transport. A Donnan steric pore model, based on the application of the extended Nernst-Planck equation and the assumption of a Donnan equilibrium at both membrane-solution interfaces, is used. The study is focused on the transport of symmetrical electrolytes (with symmetric or asymmetric diffusion coefficients). The influence of effective membrane charge density, permeate volume flux, pore radius and effective membrane thickness to porosity ratio on the contribution of the different transport mechanisms is investigated. Convection appears to be the dominant mechanism involved in electrolyte transport at low membrane charge and/or high permeate volume flux and effective membrane thickness to porosity ratio. Transport is mainly governed by diffusion when the membrane is strongly charged, particularly at low permeate volume flux and effective membrane thickness to porosity ratio. Electromigration is likely to be the dominant mechanism involved in electrolyte transport only if the diffusion coefficient of coions is greater than that of counterions.

Journal Article↗
PubMed2002

Electrokinetic characterization of porous plugs from streaming potential coupled with electrical resistance measurements.

The zeta potential of mixed nickel-iron oxide particles is evaluated by a new laboratory instrument. This latter allows the measurement of streaming potential together with the electrical resistance of porous plugs. The conductivity of electrolyte inside plug (pore conductivity) is deduced from electrical resistance measurements and is used together with streaming potential to evaluate the zeta potential by accounting for the surface conduction phenomenon. It is shown that neglecting the surface conduction phenomenon leads to a substantial underestimation of the zeta potential. The coupled measurements of streaming potential and plug electrical resistance yield zeta potential values that are in very good agreement with those obtained by electrophoresis. The densification of the porous plug with increasing pressure increments is put in evidence by the decrease in measured streaming potentials. Electrical resistance measurements make it possible to account for the increase in surface conductivity resulting from the more compacted structure of the plug. By doing so, the calculated zeta potential is found to be virtually independent of the pressure difference involved in streaming potential experiments, whereas the negligence of surface conduction phenomenon leads to a decrease in the apparent zeta potential with increasing pressure level.

Journal Article↗
PubMed1999

Electrokinetic Phenomena in Homogeneous Cylindrical Pores.

The electrokinetic phenomena occurring in homogeneous cylindrical pores containing symmetric electrolytes are studied. The local relations for flow in the pores (Nernst-Planck and Navier-Stokes equations) are developed. The analysis includes a numerical solution of the nonlinear Poisson-Boltzmann equation. The integral expressions of the phenomenological coefficients coupling the solvent flow and the electrical current with the hydrostatic pressure and the electrical potential gradients are established and calculated numerically. The mobilities of anions and cations are individually specified and the electroviscous effects as well as the surface conductance are taken into account. Streaming potentials obtained from numerical calculations are compared with results given by classical relations in a range of zeta potentials and electrokinetic radii that may commonly occur in experimental investigation of micro- and ultrafiltration membranes. In this work, it is shown that classical approximated relations can give rise to very misleading conclusions and that the determination of the true zeta potential requires a full analysis (including numerical calculations) of the basic relations for flow and potential distribution in charged pores. Copyright 1999 Academic Press.

Journal Article↗
PubMed1996

Validity in nulliparas of increased beta-human chorionic gonadotrophin at mid-term for predicting pregnancy-induced hypertension complicated with proteinuria and intrauterine growth retardation.

The objective of the present study was to investigate whether increased beta-human chorionic gonadotrophin (beta HCG) plasma concentrations in an unselected population of nulliparas could predict the occurrence of complicated pregnancy-induced hypertension (PIH). The design was that of a prospective population study. It was conducted at the obstetric departments of Amiens University Hospital and Creil General Hospital on 434 consecutive nulliparas with singleton pregnancies after natural fertilization who accepted the systematic offer of trisomy 21 screening but for whom this disorder was finally estimated. Measurement of plasma concentration of beta HCG (ELISA method) was carried out between 14 and 20 weeks (mean: 17 weeks) of amenorrhea, and measurement of blood pressure and proteinuria (> 300 mg/24 h or Albustix +2) during the first, second and third term and 2-3 months after the delivery, as well as measurement of birth weight for determination of small for gestational age (SGA) babies, 37 women developed PIH, 10 without other complication, 16 with proteinuria (5 of which with SGA babies) and 11 with SGA babies. Furthermore 2 patients presented abruptio placentae without PIH. 395 women did not develop PIH including 389 normotensive women and 6 chronic hypertensive patients without superimposed toxemia. Only 1 was diabetic. None had chronic renal disease. Mean (+/- SD) levels of beta HCG were higher in PIH than in controls: 46,805 +/- 19,068 versus 23,479 +/- 13,463 IU. A pathologic threshold was chosen as the mean for the whole population + 1 SD: 25,613 + 15,479 = 41,082 IU. Elevated levels (above this value) were significantly associated with isolated PIH or PIH complicated with proteinuria and/or with SGA babies. The positive predictive value of this criterion was respectively 11, 15 and 12% for each of these complications. The relative risk (and 95% confidence limit) of women with elevated beta HCG for each of these complications was 20 (6-79), 11 (4-43) and 22 (7-93). Elevated plasma beta HCG found around 17 weeks of amenorrhea predicts PIH complicated with either proteinuria or SGA babies with a positive predictive value comparable to that of the best and earliest test proposed up to now to select nulliparas at high risk of preeclampsia, namely the abnormalities of the Doppler waveforms of the uterine arteries. Since this test is simpler to perform, it represents the most convenient method to screen a population of nulliparas for evaluation of the benefits of low-dose aspirin.

Adult↗
PubMed1996

[Detection of multivessel lesions after myocardial infarction. Improvement of the predictive value of early exercise stress test by discriminant analysis].

The aim of this study was to assess, by a discriminant analysis, the different parameters of exercise stress testing associated with multivessel disease after uncomplicated myocardial infarction and to determine whether their combination improved the diagnostic value of ST depression alone, the usual diagnostic criterion. One hundred and seventeen out of 240 consecutive pts admitted for acute myocardial infarction between october 1992 and may 1994 underwent early exercise stress testing and coronary angiography 8.5 +/- 3 days and 13 +/- 8 days respectively after infarction. The population was divided into two groups: a "study" group (pts recruited between october 1992 and october 1993) for whom a diagnostic equation had been established based on a discriminant analysis, and "a control" group (pts recruited between november 1993 and may 1994) allowing validation of the diagnostic equation. Of the 9 clinical and 14 exercise stress test variables, only 3 remained statistically significant after discriminant analysis in this study group: the number of METS achieved (p < 0.0005), maximal ST depression in V5 (p < 0.005) and maximal heart rate (p < 0.01). Using these three parameters, a discriminating equation was established in the study group and then validated in the control group. Using this equation, the percentage of pts correctly identified as having multivessel disease was 75% in the study group and 79% in the control group, whereas ST depression, the most commonly used criterion, only classified 68% of the study group and 60% of the control group correctly. This study confirmed the good tolerance of early maximal exercise stress testing after uncomplicated myo-cardial infarction. The combination of three easily discernable parameters improved the diagnostic performance of the stress test in identifying multivessel disease after myocardial infarction.

Adult↗
PubMed1996

Validation protocol of analytical hemostasis systems: measurement of anti-Xa activity of low-molecular-weight heparins.

A standard validation protocol adapted to the chromogenic assay of anti-Xa activity of low-molecular-weight heparins was used in a multicenter study to assess its suitability for comparing and evaluating analytical hemostasis systems. The protocol included: familiarization with the system (repeatability); assessment of limits of linearity, detection limits, and cross-contamination; and validation (reproducibility and accuracy of measurements of treated patients' plasmas). We calibrated the systems with the same range of lyophilized plasmas daily and evaluated repeatability and reproducibility by using a single batch of lyophilized plasmas at three anti-Xa activities. The two automated systems tested [SB 300 (Gilford) and ACL (IL)] and the two semiautomated systems [ST 888 (D. Stago) and Chromotimer (Behring)] gave similar mean values. Dispersion of results was lower with the automated systems than with the semiautomated ones, especially at low anti-Xa activities, a tendency that also was observed for reproducibility. Because each analytical system gave linear results for activities as great as 1000 IU/L, suitable sample dilution is advisable for higher anti-Xa activities. Accuracy was greater in the automated systems. We conclude that this protocol is feasible and is applicable to validation of other analytical hemostasis instruments, in particular the latest generation of fully automated instruments.

Autoanalysis↗
PubMed1996

[Nodular regenerative hyperplasia associated with primary antiphospholipid syndrome].

Nodular regenerative hyperplasia of the liver is characterized by diffuse nodularity of the hepatic parenchyma without fibrotic septa. It may be related to venous or arterial obstruction in the portal tract. We report a case of primary antiphospholipid syndrome associated with nodular regenerative hyperplasia in a 45-year old woman. The patient had an ischemic stroke, associated with an acute arterial ischemia of the left leg. She had high titers of serum anticardiolipin antibodies. Nodular regenerative hyperplasia of the liver was histologically confirmed and was associated with anicteric cholestasis. This case provides additional evidence that a thrombotic mechanism may play a role in the pathogenesis of nodular regenerative hyperplasia of the liver.

Antiphospholipid Syndrome↗
PubMed1995

[Hypertension and pregnancy. Diagnosis, physiopathology and treatment].

This review on hypertension in pregnancy focuses mainly on the pathophysiology and prevention of pregnancy induced hypertension which, when associated with proteinuria, is usually called preeclampsia. Rather than a genuine hypertensive disease, preeclampsia is mainly a systemic endothelial disease causing activation of platelets and diffuse ischemic disorders whose most obvious clinical manifestations involve the kidney (hence the proteinuria, edema and hyperuricemia), the liver (hence the hemolytic elevated liver enzymes and low platelets, or HELLP syndrome), and the brain (hence eclamptic convulsions). Hypertension is explained by increased vascular reactivity rather than by an imbalance between vasoconstrictive and vasodilating circulating hormones. This increased reactivity is due to endothelial dysfunction with imbalance between prostacyclin and thromboxane A2 and possibly dysfunction of NO and endothelin synthesis. The aggressive substances for endothelium are thought to be of placentar origin and the cause of their release is explained by placentar ischemia related to a defect of trophoblastic invasion of the spiral arteries. The etiology of this latter defect is unknown but involves immunologic mechanisms with genetic predisposition. The only effective treatment for PIH is extraction of the baby with the whole placenta. The decision for extraction is often a very delicate obstetric problem. Antihypertensive drugs are mainly indicated in severe hypertension (> 160-100 mm Hg), with the aim of preventing cerebral hemorrhage in the mother, but have not been shown to improve fetal morbidity or mortality. Eclamptic seizures can be prevented and treated more effectively with magnesium sulfate than with diazepam or phenytoin. Prevention of preeclampsia remains the main challenge. Whereas antihypertensive drugs are ineffective, calcium supplementation and low dose aspirin have proven effective but mainly in selected populations with a relatively high incidence of preeclampsia (> 8-10%). In multiparas the selection of such a high risk population is relatively easy when at least 2 (or 1?) previous pregnancies were complicated with early preeclampsia and/or intrauterine growth retardation. In nulliparas the selection of the high-risk population is still a subject of research. The 2 most promising criteria are abnormal Doppler velocimetry of the uterine arteries at around 20 weeks of amenorrhea, and abnormally high plasma levels of beta HCG at 17 weeks of amenorrhea.

Adult↗
PubMed1994

[Optimization of enoxaparin dose in the prevention of coagulation in the circuits of hemodialysis: results of a multicenter study].

In order to define the optimal dosage of a low molecular weight enoxaparine (Lovenox) in the prevention of clotting in extracorporeal circulation during hemodialysis, a multicentre trial was conducted in 72 patients dialysed in seven hemodialysis units. During three weeks, these patients received as antithrombic treatment a single injection of enoxaparine at the beginning of the session. The initial dose fixed by previous data concerning dialysis with high hemorrhagic risks patients was 0.5 mg/kg (50 U1 Anti-Xa/kg). According to the evaluation of thrombotic manifestations during a 4 hour dialysis, the dosage was progressively increased if necessary for each patient. For 41% patients, the initial dose of 0.5 mg/kg was maintained along the whole study; 59% patients needed higher dose, between 0.6 and 0.9 mg/kg. The mean dose for the whole patient population at the end of the study was 0.62 +/- 0.16 mg/kg. No complication nor side effect was noted. The influence of blood flow, nature of dialysis membrane, level of hematocrit was studied. In conclusion, 0.5 mg/kg of enoxaparine can prevent thrombotic manifestations in almost half of chronic hemodialysed patients with good results. Further studies could precise the place of personal or technical parameters in the choice of the optimal dose for each patient.

Adult↗
PubMed1992

[Plasma beta chorionic gonadotropin between 14 and 20 weeks of amenorrhea: a sign of pregnancy-related hypertension].

A defect of placenta maturation has been described in hypertension of pregnancy. Plasma beta chorionic gonadotropins (beta HCG) of placental origin rise at the onset of pregnancy and reach a peak between 9 and 10 weeks of amenorrhoea. As we were making systematic assays between 14 and 20 weeks in a trisomy detection programme, we looked for differences in plasma beta HCG levels between women with pregnancy-induced arterial hypertension and pregnant women with normal blood pressure. We also studied the predictive value of such assays. Pregnancy-induced hypertension was found in 6 women in a population of 89 nulliparas and in 12 women in a population of 163 multiparas. beta HCG levels were significantly higher in women who later developed hypertension among both nulliparas (52,833 +/- 19,538 IU vs 24,499 +/- 16,485 IU) and multiparas (50,558 +/- 23,597 IU vs 20,911 +/- 11,677 IU). In nulliparas, taking 43,000 IU as threshold of pathology we found that the predictive value of beta HCG was higher than that of other tests which had gone through controlled studies (sensitivity 67 percent, specificity 91.6 percent, positive predictive value 36 percent, negative predictive value 97.4 percent, relative risk 5.4). In multiparas, taking 38,000 as threshold and combining this marker with obstetrical history it was possible to predict the occurrence of hypertension more precisely than with other markers which had gone through controlled studies (sensitivity 66.7 percent, specificity 98 percent, positive predictive value 61.4 percent, negative predictive value 97.3 percent, relative risk 8.4).

Adult↗
PubMed1991

Atrial natriuretic factor in pregnancy and pregnancy-induced hypertension.

In normal pregnancy, cross-sectional clinical data do not consistently show plasma ANF concentration differences between early pregnancy and the nonpregnant state. Sequential data in the baboon (but not in rat) show a significant decrease in plasma ANF concentration and in cardiac filling pressures in early pregnancy. The latter data support the view that pregnancy is an underfill state secondary to a primary vasodilatation. Cross-sectional and longitudinal studies in normal pregnancy in humans show that plasma ANF levels tend rise to values that are, in the third trimester, higher than in the nonpregnant state. However, late postpartum sequential data (1.5-3 months) in humans do now show a significant drop in plasma ANF concentrations, suggesting that plasma ANF is not actually increased in normal pregnancy. In the baboon (but not in the rat) there is a steady rise in plasma ANF levels to values that are significantly higher in third trimester than before pregnancy. These data suggest that in human pregnancy, in contrast with the baboon, the plasma volume expansion induced by normal pregnancy is not sensed as such by the atria probably because of an isopressive adaptation of plasma volume to an enlarged vascular bed. However, acute decrease or increase of venous return induced by low sodium diet, changing position or infusion of isotonic saline are sensed as such by the atria in normal pregnancy as in the nonpregnant state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Plasma atrial natriuretic factor and urinary excretion of a ouabain displacing factor and dopamine in normotensive pregnant women before and after delivery.

Estimation of urinary excretion of a ouabain displacing factor and dopamine was carried out immediately before delivery, and 7 days and 70 to 90 days after delivery in 12 normotensive pregnant women. Simultaneous estimation of plasma 99-126 atrial natriuretic factor, plasma renin activity, and plasma aldosterone were also undertaken. The data were compared with those obtained in a group of nonpregnant normotensive women (n = 14) and a group of pregnant normotensive women in the early phase of the third trimester (n = 14). Urinary ouabain displacing factor and dopamine levels were significantly higher in the early phase of the third trimester, as compared with nonpregnant women. But immediately before delivery, ouabain displacing factor excretion had fallen below nonpregnant values and dopamine excretion had dropped to control values. Both remained low after delivery. Plasma atrial natriuretic factor was higher in pregnant women, as compared with nonpregnant controls and remained high just before delivery and 7 and 70 to 90 days after delivery. Plasma renin activity and plasma aldosterone levels were higher during pregnancy and had fallen to nonpregnant values 7 days post partum. This drop in plasma renin activity and aldosterone by 7 days post partum, in contrast with the unchanged high values of atrial natriuretic factor, may contribute to negative sodium balance after delivery. It is concluded that there is considerable discrepancy in natriuretic and antinatriuretic factors before and after delivery.

Atrial Natriuretic Factor↗
PubMed1990

Systemic AA amyloidosis induced by liver cell adenoma.

Systemic AA amyloidosis is a rare complication of benign tumours. This report describes a patient with hepatocellular adenoma associated with reactive AA amyloidosis. He had a nephrotic syndrome with deteriorating renal function and an increase of serum concentrations of acute phase proteins, mainly C-reactive protein. Resection of the tumour was followed by improvement in renal function and a marked decrease of the serum concentrations of acute phase proteins.

Amyloidosis↗