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Biomedical subjects

A Layet

Publications and source records attributed to A Layet.

6 recordsLinked to original sources
PubMed1995

Phenobarbital in hair and drug monitoring.

Phenobarbital analysis was performed in vertex hair of patients by gas chromatography mass spectrometry (GC/MS). After washing with dichloromethane, about 250 mg were ground to dust in a ball mill. A 50-mg sample was stirred mechanically for 10 min with 3 ml of NH4Cl/HCl buffer (pH 2.0) containing phenobarbital D5. A solid phase extraction was performed (extrelut Merck) and elution was achieved with chloroform/isopropanol/n-heptane (50:17:33; v/v). A full scan (40-240 uma) acquisition was realized by GC/MS with an ion trap (ITD 700 Finnigan) using a DB5-MS chromatographic column. Quantification was achieved by integrating dominants ions (phenobarbital, 204; phenobarbital D5, 209). Compared to serum, hair concentrates phenobarbital during anti-epileptic therapy (average value 36.4 ng/mg, n = 40 vs. 18.7 mg/l, n = 23). A group correlation exists between phenobarbital in hair and phenobarbital in serum, and between phenobarbital in hair and clinic observation in some typical cases. Phenobarbital in hair yields good information over a long period, especially when blood collection has not been made, when clinical disorders are observed on long-term therapeutic observance.

Adult↗
PubMed1986

[Topographic aspects of visual evoked potentials recorded after flash-pattern stimulation in normal subjects].

Visual evoked responses have been recorded on 14 leads placed on the scalp. They were localised on the central, parietal, temporal and occipital regions. The common reference was linked-ears. The stimulus consisted of a flash pattern. The size of the pattern and of each square was respectively of 20 degrees and 30 min. The stimulation of the total visual field had evoked two families of curves. One of these types of curves was posterior (occipital, temporal and parietal) and consisted in a positive, negative, positive wave (100, 136, 200 msec on average) and the second type was localised on the central leads and much more rhythmic than the posterior response. The initial complex (negative, positive, negative, positive: 70, 92, 120, 178 msec) was followed by a slow after-discharge. The half-field stimulation evoked a P100 component on the contralateral posterior leads, but this P100 was less prominent on the ipsilateral posterior leads. The modifications were particularly evident at the level of the temporal posterior electrodes. This P100 component was the only wave to be modified by half-field visual stimulation. The posterior N136 and P200 wave and all the rhythmic central response were exactly the same with half or total visual field stimulation. The results have obviously shown that the different waves of the visual evoked responses are not coming from the same sources. The interpretation of multichannel evoked recordings was therefore very difficult.

Adult↗
PubMed1985

[Flash-pattern visual evoked potentials and limited lesions of the occipital lobe].

Four patients with restricted lobe lesions and one patient with large occipital lesions were selected for VEP studies to full-field and half-field flash pattern stimuli. The abnormalities of the responses were more important with full-field stimuli. In three patients with inner side occipital lobe damage, the P100 component disappeared ipsilaterally to the lesion, but N140 remained normal on bilateral occipital leads. In one patient with outer side occipital lobe damage, P100 was normal on bilateral occipital leads, but N140 disappeared ipsilaterally to the lesion. In one patient with large occipital lesion, P100 and N140 both disappeared ipsilaterally to the lesion. It appears that the P100 component is related to the inner and that N140 is related to the outer area of the occipital lobe.

Adult↗
PubMed1985

[Cerebral embolism without apparent cause: angiographic study of minor predisposing cardiac anomalies. Prospective study of 64 patients].

The heart is the source of about 50 p. 100 of cerebral emboli. In the absence of clinically obvious cardiac disease, the heart is nevertheless suspected to be the origin, especially in young patients without atherosclerosis. Cardiac catheterisation and angiography were performed systematically to detect minor predisposing cardiac abnormalities which did not appear on standard clinical examination, and which could increase the risk of recurrent embolism. 64 patients aged 21 to 69 years were studied prospectively a few weeks after a cerebral vascular accident attributed to embolism on the results of complementary neurological investigation, or, more rarely, after systemic embolism to one of the limb arteries. Clinical examination, chest X-ray and the electrocardiogram were normal in all cases. The investigation consisted in right and left cardiac catheterisation, global angiography after right atrial injection, selective left ventricular angiography and coronary angiography in all patients over 40 years of age. Unsuspected cardiac abnormalities were detected in 39 of the 64 patients (60 p. 100); the main abnormalities were mild or moderate mitral valve prolapse (30 p. 100 of cases) and slight decreases in left ventricular contractility possibly related to a minor form of cardiomyopathy (23 p. 100 of cases). Ambulatory 24 hour monitoring showed supraventricular arrhythmias in 30 p. 100 of cases. The results of echocardiography were disappointing in the diagnosis of these minor abnormalities. In conclusion, cardiac abnormalities were detected in the majority of cases of cerebral embolism by cardiac catheterisation. These results support the indications for long-term anticoagulant and/or anti-arrhythmic treatment in these patients.

Adult↗
PubMed1984

[Dissociation of visual evoked responses to hemi-field or full-field flash-checkerboard stimulation].

Unexpected visual evoked responses (VERs) were recorded in 5 subjects with tumoral, ischemic or hemorrhagic lesions of the retrochiasmatic visual pathways. The flash pattern stimulation was always binocular and involved full-field and half-field stimuli. In these 5 cases, the total field VER was asymmetrical with anomalies on the affected occipital region. However half-field VERs P100 contralateral to the stimulus were noted both on the normal and on the affected occipital region. One can ask if this is not an electrophysiological equivalent of the clinical relative hemianopsia.

Adult↗