PubMed Health⌕ Search

Biomedical subjects

S Legrand

Publications and source records attributed to S Legrand.

18 recordsLinked to original sources
PubMed2000

[Leukocyte adhesion on a fibrinogen-coated surface under static conditions: experimentation and creation of a model].

The adhesion of polymorphonuclear leukocytes (PMNs) on the vascular endothelium is a complex process that occurs during different biological and pathological events and involves numerous molecules. The adhesion cascade is induced after PMN stimulation by various molecular or cellular signals. Fibrinogen is one of the substrates for CD11b/CD18 B2-integrins expressed at the PMN surface; fibrinogen-neutrophil binding is induced by inflammatory reactions. In order to understand this process, we have carried out studies on the basis of preliminary experiments on red blood cells and synthetic particles. The modelization of quiescent PMNs adhesion on a fibrinogen substrate was investigated with a sedimentation cell chamber. Two different physiological conditions were tested: the activated state of PMN by a synthetic pro-inflammatory activator (FMLP). The activated state of PMNs was both quantified by flow cytometry and controlled by fluorescence microscopy. The results suggest that quiescent neutrophils deposit in accordance with the ballistic deposition model. This random adsorption model differs from random sequential adsorption (RSA) in that the cells arriving at the surface are able to roll along cells previously adsorbed introducing the notion of gravitational attraction of cells. The preliminary results obtained with stimulated PMN do not allow to choose between one of this two deposition models. Nevertheless, the qualitative and quantitative effects of FMLP on neutrophils were demonstrated by modifications of adhesion molecules expression.

Antigens, CD↗
PubMed1999

[Hemorheology and vascular endothelial cells].

The vascular endothelium is a biologically active monolayer of cells providing an interface between the blood flow and tissues. Vascular Endothelial Cells (VEC) have two functional states. The endothelium is normally anti-thrombotic and anti-adhesive to ensure blood fluidity. During aggressions, such as atherosclerosis, inflammation states, metabolic diseases (through chemical or mechanical stimuli), VEC can reverse its functions by expressing stored material or by slower involvement of previously are repressed genes. Endothelial cells have three types of anti-thrombotic properties: vaso regulating properties: VEC release vasomotor components, such as endothelin (vasoconstriction), prostacyclin and nitric oxide, (vasodilatation). Endothelial cells also have antithrombotic and hemostatic properties. They express proteoglycans on their surface, including some negative-charge, plasminogen, sulfate glycosaminoglycans (heparan-sulfate), and secrete plasminogen tissular activator (t-PA) and tissular factor inhibitor. One fundamental action of the endothelium in that area is the production and expression of thrombomodulin, a thrombin receptor. This function has a major anticoagulation effect, controlling continual thrombin generation at the sub-endothelium and blood cell interface. Moreover, endothelial cells show anti-adhesion properties. During cardio-vascular diseases, all of these properties may be reversed. Thus the VEC have a determinant role in hemodynamic control through these various metabolic activities, such as control of homeostasis, vascular tone, blood fluidity, coagulating properties, cellular adhesion. Otherwise, many studies have demonstrated that local blood flow conditions have a crucial role on the VEC properties (mechanoactivation and mechanotransduction concept). In conclusion, knowledge of all the properties of the endothelial cells and control of the phenomena which define their functions is a key element in understanding cardiovascular diseases.

Animals↗
PubMed1999

Hemorheology and vascular endothelial cells.

The vascular endothelium is a biologically active monolayer of cells provided an interface between blood and tissues. Vascular endothelial cells (ECs) have two functional states, which are allowed by their different properties: (i) vaso regulating properties: ECs releases vasomotor components, as endothelin (vaso constriction), prostacyclin and nitrite oxide (vaso dilatation); (ii) antithrombotic and hemostatic properties; and (iii) anti-adhesion properties. The endothelium is normally antithrombotic and anti-adhesive to ensure blood fluidity. During many cardio-vascular diseases, these properties may be reversed. Thus, the ECs have a determinant role in hemodynamic control through these various metabolic activities. Otherwise, many studies have demonstrated that local blood flow conditions have a crucial role on the EC properties (mechanotransduction concept). The knowledge of the properties of ECs and the control of the phenomena which define their functions is a key element in the cardiovascular diseases understanding.

Animals↗
PubMed1999

[Seroprevalence of hepatitis B and C viruses in a psychiatric institution].

Many patients admitted to psychiatric institutions have a history of risk factors for contamination with the hepatitis B and C viruses (HBV and HCV). Immunization policies for psychiatric institution patients are not widely know. A study conducted in a 600-bed psychiatric institution in Paris, France, to evaluate the proportion of potentially contaminating patients at admission, as well as immunization use in HBV-negative patients. Serologic markers for the HBV and HCV were looked for prospectively in all patients admitted over a two-month period. Immunization use was evaluated in the patients who had a first serologic test in 1995 or 1996 and follow-up tests until the end of 1997. The prospective part of the study demonstrated preadmission exposure to the HBV in 23.0 +/- 6.0% of patients. This proportion was larger in men (26.0%) than in women (14.8%), although the difference was not statistically significant (P = 0.10). Four patients (2.0%) tested positive for the HbS Ag. Among the HBV-negative patients, 13.0% received the vaccine; all had protective antibody levels. These patients were younger and more likely to be first-time admissions (18.4% vs 3.6%, P < 0.01). HCV seroprevalence was 6.0%. Serologic tests for the HBV were requested for 327 patients between January 1995 and december 1996. Among the patients who were seronegative at admission and received follow-up at the study hospital, only 13.8% were immunized at this hospital. Of the HCV-positive subjects, 63.3% were also HBV-positive. None of the HCV-positive HBV-negative subjects received immunization subsequently. Six to eight per cent of patients admitted to the study hospital are potentially contaminating for the HBV or HCV. The level of hepatitis B vaccine use is too low, particularly in high-risk patients. These data indicate a need for policies aimed at effectively preventing HBV and HCV transmission (information, education, immunization campaigns), both during the psychiatric institution stay and after discharge.

Adult↗
PubMed1999

Modelisation of leukocyte adhesion on a fibrinogen coated surface in static conditions.

The adhesion of polymorphonuclear leukocytes (PMNs) on the vascular endothelium is a complex process that occurs during biological and pathological events and involves a large family of molecules. This phenomenom could be approached by a modelisation study of the adhesion of PMNs on a biological substrate, fibrinogen. Two different physiological conditions were tested such as the activated state of PMNs with a synthetic pro-inflammatory activator (N-Formyl-Methionyl-Leucyl-Phenylalanine, FMLP). The activated state of PMNs was both quantified by flow cytometry and controlled by fluorescence microscopy. The results suggest that quiescent PMNs deposit in accordance with the ballistic deposition model. The preliminary results obtained with FMLP-stimulated PMNs show a different deposit process compared to quiescent PMNs but do not allow to determine exactly a deposition model.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed1990

Beta-adrenoceptor blockade potentiates exercise-induced release of atrial natriuretic peptide.

The effect of a non selective and a cardio-selective beta-blocker on basal and exercise-stimulated plasma atrial natriuretic peptide concentrations in healthy volunteers has been studied. Nine healthy volunteers received single oral doses of 5 mg tertatolol, 100 mg atenolol or placebo, at one week intervals, in a double blind cross over trial. At rest plasma atrial natriuretic peptide, aldosterone, antidiuretic hormone and cyclic GMP concentrations and plasma renin activity were not modified by the treatments. During exercise plasma atrial natriuretic peptide concentrations were significantly increased by each treatment, the increment being significantly greater on beta-blockers than on placebo. The rise in atrial natriuretic peptide was 72% after placebo (from 24 to 42 pg/ml), 184% after atenolol (from 30 to 86 pg/ml), and 183% after tertatolol (from 34 to 95 pg/ml), respectively. Thus, the study has shown that in healthy subjects the plasma natriuretic peptide concentration is increased by exercise and that the increase is considerably and equally potentiated by selective and non selective beta-adrenoceptor blockade. The effect may be mainly due to a reduction in ventricular contractility with an increase in atrial pressure. The beta-blockers did not influence the resting plasma atrial natriuretic peptide levels, which suggests that in healthy subjects basal atrial natriuretic peptide secretion is not controlled via beta-receptors.

Adrenergic beta-Antagonists↗
PubMed1988

Effects of ciclosporin on plasma renin activity, catecholamines and prostaglandins in patients with idiopathic uveitis.

Animals and humans undergoing treatment with ciclosporin (CS) show a reversible increase in renal vascular resistance and a decrease in glomerular filtration rate. The causes of these abnormalities have not yet been established. We evaluated the effects of a 1-week treatment with CS on creatinine clearance, renal arachidonic acid metabolites, plasma renin activity (PRA), plasma aldosterone levels, urinary excretion and plasma levels of catecholamines in 7 patients with idiopathic uveitis. We show that CS treatment induces a significant (p less than 0.05) decrease in creatinine clearance (from 132 +/- 0.5 to 108 +/- 8 ml/min); urinary 6-keto-PGF1 excretion (from 17.8 +/- 4.9 to 10.9 +/- 3.3 ng/mmol creatinine), urinary thromboxane B2 excretion (from 7.0 +/- 1.0 to 3.6 +/- 0.9 ng/mmol creatinine), upright PRA (from 4.2 +/- 0.9 to 2.3 +/- 0.8) and supine PRA (from 2.0 +/- 0.5 to 1.1 +/- 0.3). We found no change in plasma aldosterone levels and plasma levels and urinary excretion of catecholamines. We suggest that the reversible renal vasoconstriction observed in patients treated with CS may be induced by inhibition of renal prostacyclin synthesis. In this setting inhibition of PRA and angiotensin II formation may impair autoregulation of effective filtration pressure and therefore glomerular filtration rate.

Adult↗
PubMed1988

[Atrial natriuretic factor, catecholamines and the renin-angiotensin system in cardiac insufficiency. Relation to hemodynamic parameters].

Plasma concentrations of atrial natriuretic factor (ANF), catecholamines (adrenaline, noradrenaline, dopamine) and aldosterone, and plasma renin activity (PRA) were measured in a group of 20 patients with moderate to medium heart failure (NYHA class II 7 patients, class III 13 patients), 24 hours after treatment was discontinued. Compared with a control group, plasma concentrations of ANF (p less than 0.01), noradrenaline (p less than 0.05), aldosterone (p less than 0.01) and PRA (p less than 0.01) were significantly increased. There was a significant difference between class II patients and class III patients in plasma ANF (p less than 0.01) and noradrenaline (p less than 0.02) concentrations, but not in PRA and aldosterone levels. A significant correlation was observed between plasma ANF concentration and left ventricular end-diastolic pressure (r = 0.68, p less than 0.001), pulmonary arterial pressure (r = 0.59, p less than 0.01), pulmonary capillary pressure (r = 0.51, p less than 0.02), cardiac index (r = 0.46, p less than 0.05) and left ventricular end-diastolic volume (r = 0.50, p less than 0.05). However, ANF concentration was not correlated with mean right atrial pressure. Plasma adrenaline concentration correlated with systemic arterial resistance (r = 0.80, p less than 0.001), pulmonary arterial pressure (r = 0.57, p less than 0.02), mean pulmonary capillary pressure (r = 0.62, p less than 0.001), cardiac index (r = 0.53, p less than 0.05) and left ventricular end-diastolic pressure (r = 0.58, p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

[Aldosterone in primary hyperaldosteronism].

The conditions which must be respected to ensure the validity of the biochemical diagnostic criteria of primary hyperaldosteronism, conditions of blood sampling, timing posture and age of the patient, sodium intake and intercurrent drug therapy. As none of the tests is 100 p. 100 specific in distinguishing adrenal adenoma from hyperplasia, an association of several investigations has to be used. In cases of adenoma, the authors recommend the investigations which demonstrate the autonomy of secretion and the prevalence of circadian rhythm over the influence of change in posture. The measurement of aldosterone levels may be completed by that of its precursor, 18-hydroxy-corticosterone (18 OH CS).

Adenoma↗
PubMed1979

[Adrenocortical function in hyperprolactinemia. The study of glucocorticoids, mineralocorticoids and androgens in chronic and acute hyperprolactinemias (author's transl)].

Glucocorticoids, mineralocorticoids, and adrenal androgens were studied in 3 groups of patients: control subjects (group I), hyperprolactinemic subjects (group II) and miscellaneous patients including chromophobe adenomas and normalized hyperprolactinemic subjects treated with Bromocriptine (group III). All the patients were studied in the basal state and under various conditions: Metyrapone, ACTH, TRH for glucocorticoids, ACTH, TRH, saline perfusion for mineralocorticoids, ACTH and TRH for androgens. It is concluded that: the adrenal secretion of glucocorticoids, mineralocorticoids and androgens is not altered under basal conditions in chronic hyperprolactinemia nor during dynamic tests in chronic hyperprolactinemia (prolactin adenoma) nor in acute hyperprolactinemia (induced by TRH).

Acute Disease↗
PubMed1977

Radioimmunological determination of urinary tetrahydroaldosterone.

A method is presented for radioimmunological determination of 3alpha, 5beta-tetrahydroaldosterone. It is based upon the reactivity of this steroid with an antiserum induced by the 3-carboxymethyloxime of 18, 21-aldosterone diacetate conjugated with bovine serum albumin. One hundred microliters of urine enzymatically hydrolyzed with an helix pomatia preparation, containing tritiated tetrahydroaldosterone for the yield calculation, were extracted with dichloromethane and chromatographed on a small celite column. The yield after extraction and chromatography was 64 +/- 17%. The radioimmunological determination was carried out in a conventional manner. The method is specific, sensitive (10 pg/tube), exact, reproducible, very simple and extremely rapid. The results showed good agreement with values given by a colorimetric method (p less than 0.001). The median value measured in 45 healthy adult subjects under standard sodium diet was 53.3 microgram/24h (95 % of the population within a 16.6 to 131.1 microgram/24h range). In 78 cases of adrenocortical insufficiency, 60 cases of obesity and 28 cases of hypokalemia, the median values (and the ranges : microgram/24h) were respectively 7.7 (1.0 - 51.0), 80.9 (17.0 - 503.0) and 64.3 (8.0 - 181.0). In 330 hypertensive patients the excretion of tetrahydroaldosterone exceeded the normal range in 115 cases (35%) with a median of 199.7 microgram/24h (131 to 620 microgram/24h).

Aldosterone↗
PubMed1976

[Radioimmunoassay of tetrahydroaldosterone in urine].

A radioimmunoassay for urinary tetrahydroaldosterone is described. An antiserum, elicited by a 3-carboxy-methyloxime 18-21 aldosterone diacetate conjugated to bovine serumalbumine, with which tetrahydroaldosterone cross reacts, is used. The method is specific, sensitive (10 pg/tube), accurate, reproducible (7%), thus allowing sufficient reliability for clinical applications. In 19 normal adults subjects under unrestricted sodium intake, the urinary tetrahydroaldosterone averaged 59,8+/-29,4 mug/24 h.

Adult↗