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Biomedical subjects

G Cheron

Publications and source records attributed to G Cheron.

At least 73 records · Page 4Linked to original sources
PubMed1991

[Pierre Robin syndrome].

During the last few years, our knowledge of Pierre Robin syndrome has benefited from advances in embryonic neurobiology. It has been shown that the syndrome is related to an anomalous development of the foetal brainstem. A multidisciplinary study makes it possible to value prospectively the various anomalies with which it may be associated and to decide on a coherent treatment. This type of management should reduce the mortality and prevent the sequelae of Pierre Robin syndrome.

Humans↗
PubMed1991

Organic acids in aqueous humour and plasma: post mortem study in infants and diagnosis of enzymopathies.

Organic acids have been determined in aqueous humour and plasma by gas chromatography-mass spectrometry in 38 cases of infant death and 4 cases of inherited metabolic disease: one had a complex fatty-acid oxidation disorder with a large urinary excretion of adipic acid, the others had a disorder of propionate catabolism with a large urinary excretion of methylmalonic acid. In each case we found in aqueous humour the abnormal metabolite present in urine. Thus aqueous humour could be a suitable material for retrospective diagnosis of inherited metabolic diseases at autopsy in sudden infant death syndrome.

Adipates↗
PubMed1991

Alloimmune neonatal neutropenia.

In three neonates, the diagnosis of anti-NA1 alloimmune neutropenia related to maternal immunization against fetal polymorphonuclear leukocytes (PMN) antigens was achieved by serum antibody screening and PMN phenotyping. All the children were small for date and exhibited bacterial infection within days 2-13. Neutropenia persisted until days 20-50. High-dose intravenous immunoglobulin G (IVIgG) was ineffective. In one case, NA1-negative PMN collected from a normal donor were infused because of infection after thoracic surgery and resulted in a sharp but transient increase in PMN counts with resolution of infection. The natural history and the management of alloimmune neonatal neutropenia are discussed.

Adult↗
PubMed1990

Ketamine induces failure of the oculomotor neural integrator in the cat.

We studied the effect of intramuscular injection of low dose of ketamine (1 mg/kg) on the spontaneous ocular movements of the cat. Ketamine is a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptors, which is used as an anesthetic agent in human surgery. We found that ketamine administration caused a failure of gaze holding: each saccade was followed by a centripetal post-saccadic drift. This defect was selective: the dynamics of the saccades was not altered (the amplitude/maximum velocity relationship was unaffected by ketamine at the dose of 1 mg/kg). We postulated that the observed effect was due to the fact that NMDA receptors were implicated in the network of the oculomotor neural integrator that converted activity related to the saccade (pulse signal) into activity responsible for gaze holding (step signal).

Animals↗
PubMed1990

Hysteresis of plant cell-wall beta-glucosidase.

A transient-kinetic study of beta-glucosidase from soyabean cell walls was performed with the use of a stopped-flow apparatus. The progress curve of the reaction exhibits a 'slow' burst of about 1 s before the steady state is reached. In the time scale investigated this burst may be accounted for by only one exponential, whose time constant varies with the substrate concentration. As this concentration is increased the value of the time constant increases at first, then decreases. Premixing the enzyme with glucose, the last product of the reaction sequence, reverses the 'slow' burst into a 'slow' lag. Taken together, these results are only compatible with a model that involves the existence of a 'slow' conformational transition of the enzyme.

Cell Wall↗
PubMed1990

[Sudden infant death syndrome].

Over the last 20 years, the sudden infant death syndrome has become the leading cause of death in infants aged one month to one year in developed countries. The SIDS Referral Centers set up in France have been assigned the task of performing thorough clinical, metabolic, infectious and histologic studies. This post-mortem evaluation, whose results are difficult to interpret, is undertaken in an attempt to discriminate between the multiple causes of conditions present at the time of death. This classification task will improve the definition of a number of risk factors. Among these factors, prematurity, perinatal distress requiring resuscitation, and an unfavorable sociocultural environment are often mentioned. Other factors, including intrauterine growth retardation, dysmorphic disorders, impaired regulation of ventilation, heart rhythm anomalies, and inherited defects in fatty acid metabolism are still under study since they are all infrequent. Various combinations of these factors may result in increased vulnerability to stress during the first months of life, the period when SIDS is most common. This ongoing research is indispensable for providing advice and support of the family and developing appropriate individual preventive measures for newborn SIDS siblings.

Academies and Institutes↗
PubMed1989

Eye movements evoked by microstimulations in the brainstem of the alert cat.

This study maps the eye movements evoked by microstimulations in the medulla of 9 alert cats. Trains of square waves (20 microA amplitude, 0.2 msec duration, 200 Hz) were delivered through glass-covered tungsten microelectrodes (0.5-1 M omega). Movements of both eyes were recorded by the magnetic field/eye coil technique. Stimulation of the prepositus hypoglossi nucleus (PH) evoked nystagmus with ipsilaterally-directed slow phases followed by after-nystagmus with contralaterally-directed slow phases. Stimulation of the medial vestibular nucleus (MVN) induced nystagmus whose slow phases were more often ipsilaterally-directed but at time contralaterally-directed. At nearly all sites where we stimulated the reticular formation underlying prepositus and vestibular nuclei (from P4.5 to P12), we recorded versional conjugate movements. They were most often ipsilaterally-directed. Some microstimulations in the region of the medial longitudinal fasciculus evoked recentering eye movements: regardless of the initial position of the gaze (to the left as well as to the right), microstimulations given at the same place induced a movement of both eyes toward their neutral position. The amplitude of this movement was proportional to the eccentricity of the pre-stimulation position of the gaze.

Animals↗
PubMed1989

[Severe megaloblastic anemia in 6-month-old girl breast-fed by a vegetarian mother].

The case of a young girl, born to a woman who was a vegetarian for 18 years, is presented. She had been exclusively breast-fed until the age of 6 months when a severe anemia was discovered with an extremely low hemoglobin level (1.9 g/100 ml). Her physical growth and psychomotor development had been normal until 3 months of age. Bone marrow showed megaloblastosis and the serum B12 level was low (45 ng/l). B12 levels were also decreased in both parents (110 and 105 ng/l) and in the mother's milk (12 ng/l). Treatment with parenteral B12 was successful. The importance of a careful dietetic inquiry in the case of an infant with megaloblastic anemia is stressed and likewise, as a preventive measure during all normal pregnancies.

Anemia, Macrocytic↗
PubMed1988

[Comparative study of the amplitude, surface and duration of the pre- and post-imperative waves of the CNV (contingent negative variation) in a group of 40 schizophrenic and schizo-affective patients as compared with normal subjects].

In 27 normal adult subjects, pre- and postimperative phases of the CNV had an homogeneous pattern. The return to the baseline was of short duration (320 +/- 170 msec) whatever the amplitude and surface. This is in favor of an active mechanism terminating the CNV. In 27 schizophrenic and 13 schizoaffective patients, pre- and postimperative phases of the CNV were heterogeneous in character suggesting the possibility of multiple disturbances. When present, the preimperative negativity was of lower amplitude and had a delayed return to the baseline with a wider dispersion. In the patients with preimperative negativity followed by a PINV (postimperative negative variation), a linear relationship has been found between the amplitudes of the two waves.

Adult↗
PubMed1988

[The Pierre-Robin syndrome. Classification and new therapeutic approach].

Rhombencephalic failure of the suction-swallowing, excess of central and obstructive ventilatory arrests with hypoxia and hypercapnia, vagal hypertonia and esophagogastric motor abnormalities are the new clinical signs observed in children presenting with the Pierre Robin's syndrome. A therapeutic management adapted to each of the types I, II, III of the syndrome were defined and a good nursery-nursing allowed a reduction in the mortality-rate from 27 to 5%. Still considered by some as a malformative and glossoptosing disorder whose etiology is only bucco-pharyngeal in origin, this syndrome, common to numerous embryopathies, is a precocious embryonal abnormality of the brain stem neurogenesis, expressed by the dramatic failure of the physiological oro-ventilation system. This syndrome appears to be a peculiar form of dysautonomia of the brain stem development with an uncertain future, often transitory, isolated or associated but in the heart of pediatric internal medicine and its multi-disciplinarity.

Asphyxia↗
PubMed1987

Specific gating of the early somatosensory evoked potentials during active movement.

The gating effect of self-paced rapid flexion movements of the fingers on the early somatosensory evoked potentials following electrical stimulation of the median nerve at the wrist was studied in normal volunteers. Triggering of the median nerve stimulation by the EMG signals with a delay of 100 msec showed that the slow positive wave of the movement-associated potential was not directly responsible for the SEP amplitude variations observed. The nerve action potential at Erb's point as well as far-field components P9 and P11 were unchanged by the active movements. Far-field components P13-P14, which are presumably generated in the medial lemniscus, were not significantly modified. An enhancing effect on the widespread N18 component was found, which is in favour of a subcortical gating process. The parietal component N20 was unchanged by active movement interference whereas the frontal P22 component showed a marked suppression. A fronto-parietal dissociation was thus disclosed which could be in favour of separate cortical generators in the debate on the origin of SEP components. An important gating effect was observed on parietal P27 and frontal N30 components, the latter being considerably reduced in amplitude. The parietal P45 component showed no significant alteration. Each component of the early SEPs was thus distinctly influenced by the gating process during active movement interference.

Adult↗
PubMed1987

Renal involvement in juvenile chronic arthritis: clinical and pathologic features.

Over an 18-year period, renal involvement was diagnosed in 13 patients, who represent 1% of the total juvenile chronic arthritis population referred to us. All had severe arthritis. This study illustrates the importance of renal biopsy and indicates that renal involvement in juvenile chronic arthritis is a heterogeneous group of diseases, with a variety of causes. In eight patients with nephrotic syndrome, renal biopsy revealed amyloidosis. One rapidly died of diffuse amyloidosis and infection. The other seven received chlorambucil. Disappearance of proteinuria was noted in three of them. Four patients have persistent proteinuria but normal serum creatinine. It is suggested that, despite the long-term oncogenic risk of the drug, chlorambucil may be beneficial in patients with amyloid deposits. In one patient, the nephrotic syndrome was attributed to systemic lupus erythematosus, and in another, the chance association of an arthritis and nephrotic syndrome with minimal glomerular changes was considered. Although drug responsibility is difficult to determine in these patients receiving several medications in association, the renal involvement presented by the remaining three patients was probably related to drug(s). Moreover, it is possible that the effect of the association of medications is deleterious to the kidney. Drug-induced nephropathy is usually reversible when drugs are stopped. Unfortunately, because of persistent joint pain, these patients will continue to require pain-relieving drugs over prolonged periods.

Amyloidosis↗
PubMed1987

Disabling of the oculomotor neural integrator by kainic acid injections in the prepositus-vestibular complex of the cat.

1. This study was intended to test the candidature of the prepositus-vestibular nuclear complex for being the location of the oculomotor neural integrator (Robinson's integrator). 2. Microinjections of kainic acid (2 micrograms dissolved in 1 microliter) were made in awake cats. Injection sites were located either in the prepositus hypoglossi nucleus (p.h.), the medial vestibular nucleus (m.v.n.), the medial longitudinal fasciculus (m.l.f.) or in the magnocellular tegmental field of the reticular formation. 3. Theory predicts that a complete disabling of the neural integrator will cause (a) an exponential post-saccadic drift whose time constant will be 0.16 s in the dark (b) a phase lead of +93 deg as the vestibulo-ocular reflex is tested at 0.10 Hz in the dark and (c) a nearly complete abolition of the optokinetic nystagmus (o.k.n.). 4. About 1 h after a unilateral kainic acid injection in the p.h., we observed (a) a large bilateral post-saccadic drift (time constant sometimes as low as 0.2 s) (b) a large phase lead at 0.10 Hz (range: from +69 to +98 deg) (c) an abolition of the o.k.n. control injection of phosphate buffer in the p.h. did not produce any deficit. 5. A unilateral kainic acid injection in the m.v.n. induced a nystagmus followed by signs of bilateral failure of the neural integrator similar to those observed after kainic acid injection in the p.h. 6. Injection near the mid-line, between the two p.h. nuclei, induced a defect of the neural integrator less than that observed after kainic acid injection in either the p.h. or the m.v.n. Injection of kainic acid in the magnocellular tegmental field of the reticular formation did not produce any sign of failure of the neural integrator. No post-saccadic drift was observed. 7. We have concluded that (a) the p.h. nucleus is involved in the integration processing, and that (b) the m.v.n. is involved either in the integration processing or in the relaying of the output of the neural integrator to the oculomotoneurones.

Animals↗