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Biomedical subjects

S Laurent

Publications and source records attributed to S Laurent.

At least 127 records · Page 7Linked to original sources
PubMed1995

Use of Norplant contraceptive implants in the immediate postpartum period: safety and tolerance.

OBJECTIVE: Our purpose was to determine the safety and tolerance of levonorgestrel contraceptive implants (Norplant, Wyeth-Ayerst, Philadelphia) when inserted immediately post partum, to document the effects on weight and blood pressure, and to determine the side effects. STUDY DESIGN: After vaginal delivery, 250 women were randomized to receive Norplant within 48 hours of delivery (study group) or at the 4- to 6-week postpartum visit (control group). Baseline measurements were recorded and compared with those obtained at the 4- to 6-week follow-up visit. A diary was maintained by patients who recorded bleeding and side effects. Statistical analysis was performed with t test and chi 2 analysis. RESULTS: There were no episodes of acute postpartum hemorrhage or clinically significant bleeding. Compared with the control group, the immediate group reported significantly more bleeding days (p < 0.01). There was no significant difference between the two groups in the hemoglobin values obtained at 4 to 6 weeks post partum. The immediate insertion group reported significantly more headaches (p < 0.01) and acne (p = 0.01). CONCLUSION: Norplant is well tolerated and should be available for interested patients immediately post partum.

Acne Vulgaris↗
PubMed1995

Effects of antihypertensive drugs on large artery compliance.

The changes in arterial compliance following drug treatment have been studied mainly in hypertension. Physiologically, reduced arterial compliance independently affects blood pressure through an increase in systolic pressure and a decrease in diastolic pressure at any given value of mean arterial pressure. This review summarizes the pharmacological studies performed in recent years on the ability of antihypertensive drugs to modify arterial compliance. For the same decrease in mean arterial pressure, antihypertensive drugs may have differential effects improving arterial compliance (calcium channel blockers, converting enzyme inhibitors, alpha-blockers and some beta-blockers) or causing no change (dihydralazine, diuretics, propranolol) with resulting consequences on cardiac structure and function.

Antihypertensive Agents↗
PubMed1995

Distension capacity of the carotid artery and ambulatory blood pressure monitoring. Effects of age and hypertension.

In hypertension, the principal components of the mechanical stress acting on the arterial wall may be evaluated not only from the level of peak systolic and end-diastolic blood pressure but also by the level of pulse pressure and variability of blood pressure measured by ambulatory monitoring. The purpose of the present study was, in a population of 51 subjects with essential hypertension, to determine the influence of these parameters and of heart rate on the distension capacity of the common carotid artery, measured noninvasively by high-resolution echo-tracking techniques. The pulsatile change in diameter of the carotid artery diameter, estimated either in absolute or relative values, was shown to be significantly and independently correlated with four mechanical parameters deduced from daytime ambulatory blood pressure measurements: baseline diastolic blood pressure (the lower the diastolic blood pressure, the higher the distension capacity; r = -0.44; P < .001); pulse pressure (the higher the pulse pressure, the higher the distension capacity; r = 0.32; P < .024); variability of diastolic blood pressure (the higher the variability, the higher the distension capacity; r = 0.37; P < .008); and mean heart rate (the higher the heart rate, the more reduced the distension capacity; r = -0.28; P < .05). Multiple regression analysis indicated that mean diastolic blood pressure and its variability, mean heart rate, and pulse pressure acted independently on carotid artery distension, even after adjustment for age. The present study suggests for the first time that, in humans, hypertension may act on the arterial wall not only through the amplitude of peak systolic and end-diastolic blood pressure but also through several other mechanical factors involving the level of pulse pressure and heart rate and also blood pressure variability. Thus, in addition to the level of blood pressure, carotid artery distension is specifically influenced by two factors independently implicated in the epidemiologic cardiovascular risk: pulse pressure and heart rate.

Adult↗
PubMed1995

Influence of graded changes in vasomotor tone on the carotid arterial mechanics in live spontaneously hypertensive rats.

1. The contribution of vasomotor tone to the increased stiffness of carotid arteries in living spontaneously hypertensive rats (SHR) is largely unknown. Whether a reduced vascular tone is associated with an increase or a decrease in arterial stiffness in vivo remains to be determined. The goal of the present investigation was to show that a decrease in vascular tone is associated with a decrease in arterial stiffness, independent of the structural composition of the arterial wall. 2. New high resolution echo-tracking techniques were used to evaluate pulsatile changes of carotid blood pressure and diameter following transient and graded changes of vasomotor tone produced by the dihydropyridine derivative, isradipine. Treatment for 8 weeks was given to groups of SHR rats either with a low (0.6 kg day-1) or a high (2.6 mg kg-1 day-1) dose. Another SHR group received an acute dose of 2.6 mg kg-1 day-1. Results were compared to those of placebo-treated Wystar-Kyoto (WKY) and SHR rats. Whatever the dosage, acute or chronic calcium blockade caused a decrease in blood pressure which was maximal 1 h after administration and disappeared after the 16th h. Carotid arterial thickness and the composition of the arterial wall was determined from histomorphometry. 3. In placebo-treated SHR, the inverse relationship relating blood pressure to carotid arterial distensibility was significantly shifted toward higher values of blood pressure compared to the curve of normotensive placebo-treated WKY rats. The curve of SHR receiving chronically a non antihypertensive (0.6 mg kg-1 day-1) isradipine dose prolonged that of placebo-treated SHR toward lower values of blood pressure, so that carotid distensibility was significantly higher than in WKY for the same diameter and blood pressure level (145 mmHg). With administration of a chronic antihypertensive dose (2.6 mg kg-1 day-1) causing a significant decrease in arterial function. Acute antihypertensive calcium blockade with a single isradipine dose (2.6 mg kg-1 day-1) caused a similar shift in the pressure-distensibility curve toward the WKY curve although the histomorphometric composition of the arterial wall differed significantly from that of chronically treated animals. 4. The study provides evidence that, in living SHR submitted to calcium blockade, (i) a low dose of isradipine causing no substantial antihypertensive effect is associated with a significant elevation of carotid arterial distensibility for the same pressure and diameter as normotensive controls, and (ii) an acute or chronic dose causing a substantial antihypertensive effect is associated with a transient shift of the SHR distensibility-pressure curve toward a physiological arterial function, increasing carotid distensibility for the same pressure and diameter as WKY controls. Since such findings were observed independently of the histomorphometric composition of the arterial wall, they imply that the transient decrease in arterial stiffness produced by calcium blockade should involve specific changes in the connections between arterial smooth muscle and extracellular matrix.

Animals↗
PubMed1995

Structural changes and in situ aortic pressure-diameter relationship in long-term chemical-sympathectomized rats.

This study determined the effects of long-term chemical sympathectomy with guanethidine (GN) on the mechanical properties and composition of the distal abdominal aorta in Wistar rats. GN was daily administered for 3 mo (3M-GN, from 1 to 12 wk), 5 wk (5W-GN, from 7 to 12 wk), and 8 days (8D-GN, from 11 to 12 wk). All experiments were performed at 12 wk of age to avoid age differences at examination. We used a high-resolution echo-tracking system to determine in situ, in the systolic-diastolic range, the aortic diameter-, compliance-, and distensibility-pressure curves in anesthetized rats. We observed an equivalent significant fall in the tyramine pressor response in all conscious GN-treated rats. Blood pressure was not affected by sympathectomy after 8 days and 5 wk of treatment but was significantly reduced in 3M-GN rats. Chronic sympathetic denervation increased aortic diameter and compliance in 8D-GN rats, compared with those obtained at the same distending pressure in control rats, suggesting vascular smooth muscle relaxation. In contrast, in 5W-GN and 3M-GN rats, the distensibility pressure-curves were significantly shifted toward lower levels of distensibility and pressure, indicating a decreased aortic distensibility at the same level of arterial pressure. Sympathectomy produced a significant reduction in the content of elastin, one of the most distensible components of the arterial wall in 5W-GN and 3M-GN rats. These results suggest that intact sympathetic nerves are necessary to maintain normal functional and structural properties of large arteries in rat. The reduction in aortic distensibility, in long-term sympathectomized rats, could have resulted from complex interactions between local aortic denervation, change in the set point of distending pressure, and changes in aortic smooth muscle tone and/or wall composition.

Animals↗
PubMed1995

Common carotid artery stiffness and patterns of left ventricular hypertrophy in hypertensive patients.

The aim of this study was to determine the relationship between the lumen diameter and function of the common carotid artery, a vessel representative of the capacitance portion of the circulation, and the different patterns of left ventricular hypertrophy in uncomplicated essential hypertensive patients. Carotid luminal diastolic cross-sectional area, distensibility, and compliance were derived from measurements by a high-definition echotracking system. Left ventricular dimensions were from echocardiography. The 86 hypertensive patients included 31 who had never been treated (group 1), 31 in whom treatment had been stopped for at least 2 weeks (group 2), and 24 treated patients (group 3). In multivariate analysis of the population as a whole, the following relations were statistically independent of age, blood pressure, gender, and group: Left ventricular end-diastolic volume index was positively correlated to carotid luminal cross-sectional area (r = .46, P < .0001) and compliance (r = .47, P < .0001); left ventricular mean wall thickness and mass-volume ratio were negatively correlated to distensibility (r = -.68, P < .0001; r = -.46, P < .0001, respectively) and compliance (r = -.40, P < .0001; r = -.37; P < .001, respectively); and left ventricular mass index was positively correlated to luminal cross-sectional area (r = .23, P < .02) and negatively to distensibility (r = -.26, P < .01). These results indicate that geometric and functional changes in the common carotid artery accompany geometric changes in the left ventricle. More specifically, they suggest that a reduction in distensibility paralleled cardiac concentric hypertrophy and remodeling, whereas an increase in arterial volume paralleled increased left ventricular cavity size.

Adult↗
PubMed1995

Aortic distensibility and structural changes in sinoaortic-denervated rats.

The purpose of the present study was to determine the effects of chronic sinoaortic denervation on the mechanical properties and composition of the abdominal aorta in Wistar rats. We used a high-resolution echotracking system to determine in situ under physiological conditions of blood flow and arterial wall innervation the aortic diameter-, compliance-, and distensibility-pressure curves in 16-week-old anesthetized rats that had been denervated at 10 weeks of age for 6 weeks (n = 8). Compared with sham-operated rats (n = 8) we observed a marked reduction of baroreflex response and increase in overall mean blood pressure variability as measured by standard deviation and spectral analysis in sinoaortic-denervated rats. Mean blood pressure was not affected by sinoaortic denervation in both conscious and anesthetized rats. Sinoaortic denervation significantly shifted the distensibility-pressure curve toward lower levels of distensibility, indicating a decreased aortic distensibility for a given level of arterial pressure. Sinoaortic denervation produced a significant increase of aortic wall cross-sectional area and collagen content, one of the less-distensible components of the arterial wall. These results suggest that intact arterial baroreceptors are necessary for maintaining normal functional and structural properties of large arteries in rats. The reduction in arterial distensibility in chronic sinoaortic-denervated rats may have resulted from different factors, including the initial hypertensive phase, aortic wall hypertrophy, and increase in collagen content. The changes in aortic wall structure and related reduction in aortic distensibility, in addition to other mechanisms, might have been direct consequences of an increased blood pressure variability.

Animals↗
PubMed1995

Arterial wall hypertrophy and stiffness in essential hypertensive patients.

The purpose of this article is to review some clinical and fundamental evidence that hypertension-induced arterial wall hypertrophy at the site of large and medium-sized arteries is not necessarily associated with a decreased arterial distensibility and increased elastic modulus, and to demonstrate the opposing effects of aging and hypertension-induced hypertrophy on the arterial mechanics in vivo. in the studies reported here, the elastic properties of large and medium-sized arteries were noninvasively assessed from the simultaneous measurement of internal diameter and blood pressure inside the systolic-diastolic range. The distensibility of a medium-sized artery, the radial artery, in untreated essential hypertensive patients was not significantly different from that of normotensive control subjects when the two groups were compared at their respective mean arterial pressures. Despite increased wall thickness, the stiffness of the radial artery wall material, assessed by the incremental modulus of elasticity (Young's modulus), was not increased in hypertensive patients. At the site of a larger, more elastic artery, such as the common carotid artery, distensibility of hypertensive patients was significantly lower than that of normotensive subjects when the two groups were compared at their respective mean arterial pressures, but distensibility at 100 mm Hg was not significantly different between the two groups. Aging may alter distensibility independently of blood pressure, because carotid distensibility at 100 mm Hg was negatively correlated with age. In spontaneously hypertensive rats the elastic modulus of the common carotid artery wall material was not significantly different from that of Wistar-Kyoto rats at a given circumferential stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Four nucleotides are the minimal requirement for RNA recognition by rotavirus non-structural protein NSP3.

The interaction of the group A rotavirus non-structural protein NSP3 (NSP3A) with RNA has been studied in vitro. Using semi-purified NSP3A protein expressed by a recombinant baculovirus and in vitro synthesized RNA, we determined by UV cross-linking and gel retardation assays that NSP3A binds, in a sequence-specific manner, the consensus sequence (AUGUGACC) present on the 3' ends of all group A rotavirus mRNAs. Using short oligoribonucleotides, we established that the minimal RNA sequence required for binding of NSP3A is GACC. Modifications of the UGACC oligonucleotide sequence impaired binding of the protein to the RNA. Furthermore, the recombinant NSP3 protein from rotavirus group C showed specificity for the 3' end consensus sequence (AUGUGGCU) of only group C mRNAs. Sequence analysis of the NSP3 proteins did not reveal significant homologies with other RNA binding proteins, thus the NSP3 proteins of rotaviruses are the prototypes of a new kind of sequence-specific RNA binding protein.

Baculoviridae↗
PubMed1994

Antagonism between T3 and amiodarone on the contractility and the density of beta-adrenoceptors of chicken cardiac myocytes.

3,3',5-Triiodothyronine (T3), at 10(-8) M, potentiated by 26.4-30.9% the isoproterenol-mediated inotropic effect in chick embryo cardiac myocytes in culture. Amiodarone (10(-6) M) decreased this response by 44.6% only in cells cultured with serum, where the T3 concentration was 10(-13) M. Amiodarone inhibited the potentiating effect of T3. Amiodarone alone had no influence on the beta-adrenoceptor density in cells cultured in serum-free medium. This confirms that the effects of amiodarone on cardiac beta-adrenoceptors are T3 dependent. T3 increased the density of beta-adrenoceptors through two concentration ranges, with an initial 30% increase between 10(-14) and 10(-11) M, followed by a second increase until 10(-7) M. Amiodarone not only inhibited the first positive effect of T3 but also decreased beta-adrenoceptor density far below the control value. The second positive T3 effect was also inhibited by 50% by amiodarone. This study suggests that T3 might increase the number of cell-surface beta-adrenoceptors and modify their cellular traffic through at least two mechanisms, one assumed to be non-genomic, the other being genomic, and that amiodarone could affect the two mechanisms differently.

Adrenergic beta-Antagonists↗
PubMed1994

Interactions between beta-cyclodextrin and insoluble glyceride monomolecular films at the argon/water interface: application to lipase kinetics.

A study of the desorption rate of insoluble monomolecular films of oleic acid (OA), monoolein (MO), 1,2-diolein (1,2-DO), 1,3-diolein (1,3-DO) and triolein (TO) at the argon/water interface by water-soluble beta-cyclodextrin (beta-CD) is reported. The desorption of OA and MO involves probably the complexation of the single acyl chain with beta-CD and sequestering of the formed soluble OA/beta-CD and MO/beta-CD complexes from the argon/water interface. In the case of monolayers of multiple acyl chain molecules such as DO and TO, no detectable change in the surface pressure occurred after beta-CD injection. The surface rheological dilatational properties of the monolayers of DO and TO in the presence of beta-CD in the subphase were studied. The elasticity of the DO monolayer remained unchanged, whereas the decrease in the surface elasticity of the TO film was attributed to the formation of a water-insoluble TO/beta-CD complex. With the 'tuning fork' model, one acyl chain of TO can be included in the beta-CD cavity. The formed TO/beta-CD complex present at the interface retarded the propagation of the dilatational deformation along the plane of the monolayer. Schematic models have been proposed in an attempt to explain the different complexation of these lipids by beta-CD at the argon/water interface. In addition to the above results, the presence of beta-CD in the water subphase makes it possible for the first time to perform kinetic measurements of the lipase hydrolysis rates of long-chain glycerides forming monomolecular films.

Argon↗
PubMed1994

Noninvasive detection of an increased vascular mass in untreated hypertensive patients.

Structural changes of the arterial vasculature are of major pathophysiologic and prognostic significance in human hypertension. A high-resolution ultrasonic echotracking device was used to measure internal diameter and intima-media thickness of the radial artery, a medium-sized muscular conduit artery, in 60 hypertensive patients and in 40 age-matched control subjects. Of the 60 hypertensives, 33 were never treated and 27 were well-controlled by antihypertensive therapy. Radial artery mass and thickness/radius ratio were used to describe the radial artery structure. Radial artery mass was validated in vitro by comparing the weight of arterial segments to the ultrasonographic determination of their mass, calculated as: rho L(pi Re2-pi Ri2), where rho is the arterial wall density, L the length of the arterial segment, and Re and Ri the ultrasonic values of internal and external radii, respectively. Diastolic internal diameter did not differ among the three groups, but wall thickness, radial artery mass, and thickness/radius ratio were significantly higher in the untreated hypertensive group than in the control group. In treated well-controlled hypertensive subjects, radial artery mass and thickness/radius ratio were not different from that of control subjects. Among the population of untreated patients, significant univariate relations existed between radial artery mass and blood pressure and radial artery mass and age. In multivariate analysis, radial artery mass was independently predicted by mean blood pressure, age, and sex. Circumferential wall stress, calculated from diastolic internal diameter, wall thickness, and diastolic blood pressure, was not different in the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Reduction of arterial wall mechanical stress as a goal for antihypertensive therapy.

Some epidemiologic and experimental studies have raised the possibility that pulse pressure may be a determinant of vascular structure. In addition, 24-h blood pressure variability has been reported to be more closely related to the severity of target-organ damage than to casual blood pressure in hypertensive patients. These data suggest that when the effects of mechanical stress on the arterial wall are evaluated, it is necessary not only to take into account steady (i.e., mean) parameters but also to consider pulsatile parameters and the variability of steady and pulsatile parameters. Pharmacologic data suggest that reduction of pulse pressure during antihypertensive treatment may be a factor in prevention of altered vascular structure during chronic hypertension. Improving arterial compliance by specific antihypertensive treatment is a way to reduce pulse pressure and therefore to contribute to this prevention. Whether normalization of blood pressure variability by antihypertensive treatment is also a means of preventing altered vascular structure remains to be determined.

Antihypertensive Agents↗
PubMed1994

The nicardipine-isoprenaline interaction in human and guinea-pig isolated airways.

The effects of the dihydropyridine calcium antagonist nicardipine on the concentration-response curves of relaxant compounds acting through the adenylate-cyclase/cAMP system (isoprenaline, forskolin, adenosine and theophylline) or by the cGMP pathway (sodium nitroprusside) were studied on human isolated bronchus and guinea-pig isolated trachea. These effects were compared with those of nifedipine (a dihydropyridine derivative) and theophylline (a non-selective phosphodiesterase inhibitor). Nicardipine, in the range of 0.01 to 1 microM, significantly potentiated the relaxant effects of isoprenaline, forskolin, adenosine and theophylline, whereas the effects of sodium nitroprusside were significantly potentiated at 10 microM only. These results suggest that nicardipine behaves as an inhibitor of phosphodiesterases III and IV. One such effect may be involved in the potentiation of the isoprenaline relaxation of human and guinea-pig isolated airways.

Adenosine↗
PubMed1994

Recombinant rabbit hemorrhagic disease virus capsid protein expressed in baculovirus self-assembles into viruslike particles and induces protection.

VP60, the unique component of rabbit hemorrhagic disease virus capsid, was expressed in the baculovirus system. The recombinant VP60, released in the supernatant of infected insect cells, assembled without the need of any other viral component to form viruslike particles (VLPs), structurally and immunologically indistinguishable from the rabbit hemorrhagic disease virion. Intramuscular vaccination of rabbits with the VLPs conferred complete protection in 15 days; this protection was found to be effective from the fifth day after VLP injection and was accompanied by a strong humoral response.

Amino Acid Sequence↗