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Biomedical subjects

J P Mignot

Publications and source records attributed to J P Mignot.

8 recordsLinked to original sources
PubMed1996

[New hypothesis on the replication of centrioles and basal bodies].

Certain morphological data, obtained in studies of the ultrastructure of centrioles and basal bodies in cells of metazoa and protists, lead us to think that the cartwheel represents of the most appropriate organization for a self-reproducing and transmissible centriolar organizer. Centrioles and basal bodies might then not be simply the centres of replication of those organizers, but also reservoirs containing several superposed centriolar organizers, which are released depending on the requirements of the cell. As an isolated cartwheel is extremely unlikely to be detected, either in conventional electron microscopy or in immunocytochemistry, it is thus the reservoir which has so far been under consideration. Such a hypothesis would permit the explanation that biogenesis de novo and biogenesis in proximity to preexisting organelles may differ only in terms of the number of morphogenetic units involved.

Centrioles↗
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↗
PubMed1994

Elastic modulus of the radial artery wall material is not increased in patients with essential hypertension.

Hypertension is known to decrease arterial distensibility and systemic compliance. However, the arterial tree is not homogeneous, and it has been shown that the medium-size radial artery does not behave like the proximal, elastic, large, common carotid artery. Indeed, radial artery compliance in hypertensive patients (HTs) has been shown to be paradoxically increased when compared with that in normotensive control subjects (NTs) at the same blood pressure level. To determine whether this increase was due to hypertension-related hypertrophy of the arterial wall, radial artery functional and geometric parameters from 22 NTs (mean +/- SD, 44 +/- 11 years) were compared with those from 25 age- and sex-matched never-treated essential HTs (48 +/- 12 years) by using a high-precision ultrasonic, echo-tracking system coupled to a photoplethysmograph (Finapres system), which allows simultaneous arterial internal diameter, intima-media thickness, and finger blood pressure measurements. When the values for HTs were compared with those of NTs at their respective mean arterial pressures, HTs had similar internal diameter (2.50 +/- 0.56 versus 2.53 +/- 0.32 mm, mean +/- SD) and greater intima-media thickness (0.40 +/- 0.06 versus 0.28 +/- 0.05 mm, P < .001) measurements and increased arterial wall cross-sectional areas (3.79 +/- 1.14 versus 2.45 +/- 0.57 mm2, P < .001). Circumferential wall stress was not significantly different between the two groups. Compliance calculated for a given blood pressure, ie, 100 mm Hg (C100), was greater in HTs than NTs (3.46 +/- 2.41 versus 2.10 +/- 1.55 m2.kPa-1 x 10(-8), P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Measurement of the vascular mass of the human radial artery by ultrasonics].

OBJECTIVE: To determine the reproducibility of radial artery mass (RAM), in hypertensive patients. DESIGN AND METHODS: In 49 patients, RAM was measured using a high resolution echotracking device (Nius-02) which allows noninvasive measurement of diameter and wall thickness of the radial artery. RAM was validated in vitro by comparing weight of arterial segments to ultrasonographic measurement and determined as RAM = r (pi Re2-pi Ri2) where r is the arterial wall density (1.06 g/cm3), and Re and Ri are values of internal and external radii, respectively. Repeatability coefficient (RC2 = SDi2/n) was 1.3 mg. RESULTS: Blood pressure was (mean +/- SD) 146 +/- 19/85 +/- 15 mmHg, radial arterial diameter was 2,449 +/- 376 microns, radial wall thickness was 302 +/- 68 microns, RAM was 28 +/- 9 mg (range 13-43 mg). CONCLUSION: These results indicate that radial artery mass can be measured using a high resolution echotracking device.

Humans↗
PubMed1993

Spontaneous diameter oscillations of the radial artery in humans.

In this study we investigated whether there exists a periodic contractile activity of the radial artery, and we evaluated the impact of such an oscillatory behavior on the mechanical properties of this medium-sized muscular vessel. The internal diameter of the right radial artery was measured noninvasively in six healthy male volunteers aged 18-42 yr using a high-precision ultrasonic echo-tracking device. Blood pressure was simultaneously recorded on the same side at the middle finger by photoplethysmography. The electrical activity of the heart was monitored during the entire experiment by electrocardiography. The frequency components of the arterial diameter, blood pressure, and heart rate were obtained using spectral analysis. Under resting conditions, the radial arterial diameter exhibited a spontaneous oscillation with a period ranging from 45 to 70 s and an amplitude of 80 +/- 14 microns (+/- SE). No very low-frequency mode (< or = 0.02 Hz) was identified in either heart rate or blood pressure. These diameter oscillations affected the distensibility-pressure curves acquired simultaneously. Thus the 3-4% oscillatory variation in arterial diameter was paralleled by a 1.5- to 2-fold change in distensibility. These low-frequency oscillations of large arteries seem to be mediated by an intrinsic vascular mechanism.

Adolescent↗
PubMed1992

Dynamic non-invasive measurements of arterial diameter and wall thickness.

AIM: Non-invasive measurements of arterial diameter and wall thickness are critical in characterizing the onset and development of vascular disease. A precise dynamic method was proposed and tested for this purpose. DESIGN: A non-invasive method of measuring the variations in diameter and thickness of human arteries throughout the cardiac cycle was developed, using a high-precision ultrasonic echo-tracking system. An adaptive filtering technique was used to suppress artefacts caused by the layered tissue structure of the vessel wall. RESULTS: Based on decorrelation of microstructure noise, this technique improved the detectability of the wall interfaces, which allowed a determination of thickness and diameter. The accuracy and reproducibility of the method were tested by measurements of plastic films with known thicknesses. The discrepancies between standard micrometer and pulse-echo measurement were consistently less than 5 microns for film thicknesses ranging from 220 to 800 microns. The difference between two successive measurements was less than 2 microns. The identity of the measured vascular interfaces was checked in two ways. First, experiments on fixed bovine carotid arteries showed that the identified echogenic interfaces corresponded to the actual anatomical structure, as obtained by acoustic microscopy. Second, the radial artery thickness and diameter were extrapolated to obtain the change in wall volume over one cardiac cycle. The volume was found to be nearly constant, indicating incompressibility. CONCLUSION: This method will make it possible to obtain new information on atherogenesis and other vascular diseases.

Acoustics↗
PubMedDate not supplied

Noninvasive measurement of medium-sized artery intima-media thickness in humans: in vitro validation.

Recent research in ultrasound technology has led to the development of a high-resolution echo-tracking device. The present study was performed to evaluate the accuracy in the measurement of human radial artery intima-media thickness with this new device. We determined the correlation between histological and ultrasonic measurements of intima-media thickness in 15 radial artery segments obtained from the distal end of the wrist-elbow harvest for coronary bypass grafting in patients with coronary heart disease. For arterial intima-media thickness, a positive correlation was observed between ultrasonic and histological measurements (r = 0.618; p < 0.014), and the difference between ultrasound and histology measurements was 41 +/- 66 microns, with the higher measurements found by the ultrasonic device. In a subgroup of 11 patients, we determined the correlation between in vivo ultrasonic measurements of radial artery intima-media thickness at the preoperative stage and in vitro ultrasonic measurements of intima-media thickness obtained postoperatively in the same arterial segments. Internal diameter was larger in vivo than in vitro, and intima-media thickness was smaller in vivo than in vitro. The cross-sectional area of the arterial wall was calculated from internal diameter and intima-media thickness. In vitro wall cross-sectional area was correlated with in vivo wall cross-sectional area (r = 0.929; p < 0.0001). Repeatability of in vivo intima-media thickness measurements was investigated in 10 subjects through the calculation of the repeatability coefficient as defined by the British Standards Institution.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation Studies as Topic↗