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Biomedical subjects

L Pourcelot

Publications and source records attributed to L Pourcelot.

At least 91 records · Page 5Linked to original sources
PubMed1991

[HMPAO radionuclide of temporal cortex in the study of deafness].

A new method of dynamic exploration of central auditory pathway is presented, using measurement of cortical temporal perfusion variations, during auditory stimulation (tonal stimulation in normal hearing patients, electrical stimulation with promontory test in profoundly deaf patients). This study shows a perfusion increment in normal hearing and deaf patients with positive promontory test, which doesn't exist in a patient with negative promontory test. Further development of this study could help for optimization of post implantation auditory results.

Acoustic Stimulation↗
PubMed1990

[125I]MIBG uptake and release in different regions of the rat brain.

Radioiodinated m-iodobenzylguanidine [( 125I]MIBG) and tritiated norepinephrine [( 3H]NE]) uptake and release were compared, in different regions of the brain of the rat. The classification of the regions according to uptake was the same for both tracers:striatum greater than hypothalamus greater than hippocampus greater than cortex greater than brainstem. Tetrabenazine (TBZ), a granular monoamine uptake inhibitor reduced the uptake in the different regions. The inhibition rate was higher for [3H]NE uptake than for [125I]MIBG. The spontaneous release was the same for [125I]MIBG and [3H]NE and was the lowest in the striatum. The K+ stimulated release of [3H]NE was more complete than the release of [125I]MIBG and was the most important in the striatum. From these results, it is inferred that MIBG enters the brain tissue via NE uptake mechanisms. It appears that MIBG is stored in the chromaffin granules, as NE, but also in the cytoplasm. A modified molecule derived from MIBG which would cross the blood-brain barrier, would then appear as a potential scintigraphic marker of monoamine uptake, storage and release.

3-Iodobenzylguanidine↗
PubMed1990

[The contribution of color-coded Doppler in early vascular complications of kidney transplantation].

Ultrasound techniques and radionuclide studies are very often used to assess vascularization of renal transplants. Although, in acute tubular necrosis or acute rejection, it is difficult to choose between these two techniques, in 3 recent cases of renal artery thrombosis, we conclude that color coded Doppler is preferable to nuclear medicine or duplex system to diagnose this form of thrombosis.

Adult↗
PubMed1989

Visualization of the fetal circle of Willis and intra-cerebral arteries by color-coded Doppler.

We report here the visualization of the intra-cerebral vessels in a normal fetus of 28 weeks gestational age, by color-coded Doppler. The color-flow mapping method makes it possible to identify very small vessels that up to date could not be detected on B-mode imaging, and will permit new clinical and physiological studies of the circulation in specific areas of the fetal brain.

Cerebral Arteries↗
PubMed1989

Very high frequency pulsed Doppler apparatus.

A study of a method for exploration of microvessels is presented. Theoretical considerations taking into account the backscattering of ultrasound wave from a red cell and the attenuation versus frequency (up to 180 MHz) show that a frequency in the range of 80 to 120 MHz is most favorable for small depths of exploration (300 microns). The characteristics of the 113 MHz Doppler system which was built are described. The minimum detectable signal is 3 microV, the lateral resolution around 20 microns and the minimum length of the Doppler sample volume about 80 microns. The Doppler data are displayed in the form of a frequency spectrum. The first encouraging tests carried out using 20 microns rectangular glass capillary tubes and 50 to 150 microns microvessels of the mesentery of rat have demonstrated the resolution and the sensitivity of the system. A discussion illustrates the difficult problem of motion artefacts and the improvements which have to be made. From a technical point of view the authors think that it is possible to work with such a high frequency but there are two main difficulties: the processing of a very low frequency Doppler spectrum and the optimization of the probe (dimensions and shape).

Animals↗
PubMed1989

Doppler assessment of the intracerebral circulation of the fetus.

Fetal cerebral arteries have been explored during normal pregnancies (n = 40). The index of cerebral resistance (Rc) as defined by Pourcelot (Rc = (S-D)/S where S is the systolic amplitude and D is the diastolic amplitude) shows variations similar to the placental index (Rp). During normal pregnancy, the cerebral index is higher than the placental index and the cerebro-placental ratio (Rc/Rp) is greater than one. This preliminary study of the umbilical and cerebral circulation during 21 pathological pregnancies with hypertension seems to demonstrate that when fetal growth retardation is also present (n = 6) either or both of the indices Rc and Rp may be outside the normal range but the cerebro-placental ratio (CPR) is always less than one. However, a larger number of patients needs to be explored in order to evaluate the clinical usefulness of such an observation.

Adult↗
PubMed1989

Effect of caffeine on cerebral blood flow velocity in preterm infants.

A continuous-wave form Doppler monitor was used to examine the effect of caffeine on cerebral blood flow velocity (CBFV) in 7 clinically stable preterm neonates suffering from apnea. Caffeine, in the form of caffeine citrate, or saline were given intravenously at loading doses of 20 mg/kg. Every subject was his own control. Placebo (saline) was systematically injected prior to caffeine citrate. Simultaneous recording of heart rate, arterial blood pressure, respiratory rate, TcPO2, TcPCO2 were made before, then at the end of the injection, and 30, 60 and 120 min after the end of each administration of either placebo or caffeine. Compared with placebo, caffeine injection was not associated with significant changes in CBFV. An increase was found in both heart-rate and respiratory rate (p less than 0.05). Mean arterial blood pressure, TcPCO2 and TcPO2 did not change significantly. Our data suggest that a caffeine citrate loading dose of 20 mg/kg as currently used at the beginning of treatment of apnea in preterm neonates has no effect on CBFV.

Blood Flow Velocity↗
PubMed1989

Caffeine and cerebral blood flow velocity in preterm infants.

Continuous wave Doppler monitor was used to examine the effect on cerebral blood flow velocity (CBFV) of caffeine in 7 clinically stable preterm neonates suffering from apnea. Caffeine, as caffeine citrate at a loading dose of 20 mg.kg-1 BW, or saline were given intravenously. Every subject was his own control. Placebo (saline) was systematically injected prior to caffeine citrate. Simultaneous recording of heart rate, arterial blood pressure, respiratory rate, Tc PO2, and Tc PCO2 were made before, at the end of the injection, and 30, 60 and 120 min after the end of each administration of either placebo or caffeine. Compared with placebo, caffeine injection was not associated with significant changes in CBFV. An increase was found in both heart rate and respiratory rate (p less than 0.05). Mean arterial blood pressure, Tc PCO2 and Tc PO2 did not change significantly. Our data suggest that a caffeine citrate loading dose of 20 mg.kg-1 BW as currently used at the beginning of treatment of apnea in preterm neonates has no effect on CBFV.

Blood Pressure↗
PubMed1989

[Measurement of cerebral blood flow by transcranial Doppler ultrasonography in children presenting with autistic behavior. Preliminary results].

Transcranial Doppler ultrasonographic recordings of the middle cerebral arteries were performed on eight children with autistic behavior compared to eight controls. Blood flow measurements were assessed at rest and during auditory and visual stimulations. The main result was obtained during the auditory stimulations and concerned the left artery blood flow which is lower in autistics than in controls in these conditions (p less than .02). This result confirms the possibility of a left hemisphere dysfunctioning in autistics and may be related to clinical features as language disabilities and paradoxical reactivity to auditory stimuli.

Acoustic Stimulation↗
PubMed1989

[Renal leiomyoma. Apropos of a case].

Leiomyoma of the kidney is a rare tumor, for which little investigational imaging data is available, and which is poorly characterized by histological methods. We are here concerned with one case that benefitted from an extensive radiological workup, and we provide a comparison with other cases mentioned in the literature.

Diagnostic Imaging↗
PubMed1988

Comparison of MIBG and monoamines uptake mechanisms: pharmacological animal and blood platelets studies.

The uptake of MIBG, a scintigraphic agent widely used in the detection of APUD tumours, was studied with a pharmacological approach on an in vitro and an in vivo models. MIBG as well as norepinephrine (NE) was taken up by human blood platelets, a model for presynaptic nerve endings amine uptake, with a thermodependant mechanism. MIBG and NE uptake was inhibited by desimipramine and reserpine. However, MIBG but not NE uptake was inhibited by fluvoxamine, a serotonin (5HT) uptake inhibitor. This suggests that MIBG is a NE and also a 5HT uptake tracer which involves uptake one and vesicular storage mechanisms. In rats treated with 6-hydroxydopamine to induce a chemical sympathectomy, we observed an inhibition of uptake similar for MIBG and NE in the heart, the salivary glands and the spleen, but no effect was observed in the liver. Some clinical inferences to best investigate specific monoamine uptake are drawn from these results.

3-Iodobenzylguanidine↗
PubMed1988

Fetal cerebral circulation assessment by Doppler ultrasound in normal and pathological pregnancies.

During normal pregnancies (n = 40) the cerebral index (Rc = S - D/S) (with S = systolic and D-telediastolic amplitudes) is always higher than the placental index (Rp), and the cerebro/placental ratio (Rc/Rp) greater than 1. Of 29 pregnant women with hypertension (including two twins), 17 delivered normally (Rc, Rp and CPR normal), 14 delivered an hypotrophic fetus, in 12 out of these 14 pregnancies one of the two indices (Rc or Rp) was abnormal and the cerebro/placental ratio, CPR, was always less or equal to 1. CPR sensitivity was 86% the specificity 100%. In 11 pregnancies with idiopathic fetal-growth retardation, the CPR was less or equal to 1 in eight cases (73% of the cases), and greater than 1 in three cases (three false-negative results).

Cerebrovascular Circulation↗
PubMed1988

MIBG and catecholamine storage in the brain: an in-vitro study.

The uptake and release of mIBG, a tracer of the monoamine uptake and storage function, were studied on superfused rat cerebral cortex sections. mIBG was taken up and released by a mechanism comparable to that of norepinephrine (NE), but this storage appeared to be less specific for mIBG than for NE. This implies that when mIBG is used as a scintigraphic tracer of monoaminergic synaptic vesicles, imaging should be delayed long enough to ensure release of the molecule from its nonspecific binding sites.

3-Iodobenzylguanidine↗
PubMed1988

Therapeutic effectiveness of iodine-131 MIBG metastases of a nonsecreting paraganglioma.

This case report describes the treatment of the bone metastases of a nonfunctioning sympathetic paraganglioma, with [131I]MIBG. After primary tumor excision and unsuccessful external radiotherapy, the patient received three therapeutic doses of [131I]MIBG, resulting in a reduction of the number and volume of metastases, and an improvement of the general condition. At 3 yr following [131I]MIBG therapy, the patient remained in remission. [131I]MIBG appears to be an efficient and safe agent for treating malignant sympathetic paraganglioma.

3-Iodobenzylguanidine↗