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Biomedical subjects

G Chazot

Publications and source records attributed to G Chazot.

At least 55 records · Page 3Linked to original sources
PubMed1996

Brain responses to detection of right or left somatic targets are symmetrical in unilateral Parkinson's disease: a case against the concept of "parkinsonian neglect'.

Signs of attentional dysfunction mimicking spatial neglect have been described both in humans with lateralised Parkinson's Disease (PD) and in animals with MPTP-related hemiparkinsonism. Such deficits have been attributed to dopamine loss in basal ganglia and cortical targets. However, in previous studies the existence of neglect was assumed from behavioural tests which needed a motor output, thus entailing interpretation ambiguities due to effects of directional hypokinesia. We recorded brain event-related potentials (ERPs) evoked by the presentation of target somatic stimuli to the affected and non-affected sides in 44 patients with unilateral or asymmetrical PD. The N2 and P3 ERP components were specifically analysed, since (a) they are triggered selectively by task-relevant, attended sensory stimuli; (b) their latency reflects stimulus evaluation time, independently from the execution of a motor response, and (c) they have proved to be abnormal in hemineglect syndromes due to focal brain lesions. Irrespective of the side (left or right) of motor symptom predominance there were no significant ERP differences to stimulation of the affected and non-affected limbs, nor was there any correlation between ERP latencies and the degree of dopamine-related motor impairment. The P3 latency was abnormally delayed in 23% of the patients, but there was no trend for abnormalities to concentrate on the affected side. This study does not confirm the existence of a significant attentional impairment toward the affected limb in lateralised PD, and suggests that previous clinical evidence of "neglect' behaviour in PD might be linked to directional hypokinesia, thus reflecting intentional, rather than attentional lateralised deficits.

Adult↗
PubMed1996

Slowly progressive anarthria with late anterior opercular syndrome: a variant form of frontal cortical atrophy syndromes.

We describe eight patients with slowly progressive speech production deficit combining speech apraxia, dysarthria, dysprosody and orofacial apraxia, and initially no other deficit in other language and non-language neuropsychological domains. Long-term follow-up (6-10 years) in 4 cases showed an evolution to muteness, bilateral suprabulbar paresis with automatic-voluntary dissociation and frontal lobe cognitive slowing without generalised intellectual deterioration. Most disabled patients presented with an anterior opercular syndrome (Foix-Chavany-Marie syndrome), and pyramidal or extrapyramidal signs. CT and MRI findings disclosed asymmetric (left > right) progressive cortical atrophy of the frontal lobes predominating in the posterior inferior frontal region, notably the operculum. SPECT and PET revealed a decreased cerebral blood flow and metabolism, prominent in the left posterior-inferior frontal gyrus and premotor cortex, extending bilaterally in the most advanced cases. Pathological study of two cases showed non-specific neuronal loss, gliosis, and spongiosis of superficial cortical layers, mainly confined to the frontal lobes, with no significant abnormalities in the basal ganglia, thalamus, cerebellum, brain stem (except severe neuronal loss in the substantia nigra in one case), and spinal cord. We propose to call this peculiar syndrome Slowly Progressive Anarthria (SPA), based on its specific clinical presentation, and its metabolic and pathological correlates. SPA represents another clinical expression of focal cortical degeneration syndromes, that may overlap with other similar syndromes, specially primary progressive aphasia and the various frontal lobe dementias.

Aged↗
PubMed1996

Modelization of motor nerve conduction velocities for Charcot-Marie-Tooth (Type-1) patients. CMT-France Network.

Charcot-Marie-Tooth (CMT) type-1 (CMT1) neuropathy is characterized by peripheral nerve demyelination and has been divided into several subtypes. The most frequent among these, subtype 1A, is related to a microduplication of the region p11.2 of chromosome 17. This region contains the PMP-22 gene which is involved in peripheral nerve myelination. Since motor nerve conduction velocity (MNCV) is closely related to nerve myelination, we compared type-1A patient MNCVs versus non-A CMT1 patient MNCVs, in 57 CMT1A patients and 21 non-A type-1 patients. Patients with the 17p11.2 duplication have MNCVs that are significantly more reduced (about 20 m/s) compared to patients without the 17p11.2 duplication (about 30 m/s). This study also permits a model of the MNCV in the median nerve (MedMNCV) of CMT1 patients, with age, gender and molecular status as parameters. Furthermore, in order to help clinicians to diagnose subtypes of CMT1 patients, the probability for type 1A is modeled as a function of MedMNCV only.

Adolescent↗
PubMed1996

Molecular diagnosis of Charcot-Marie-Tooth 1A disease and hereditary neuropathy with liability to pressure palsies by quantifying CMT1A-REP sequences: consequences of recombinations at variant sites on chromosomes 17p11.2-12.

The most frequent form of Charcot-Marie-Tooth disease (CMT1A; OMIM118.220) is the result of a duplication on chromosome 17 in pll.2-p12. This region contains PMP22, a gene expressed in peripheral myelin. The mutation results from an unequal crossing-over involving repeated sequences, CMT1A-REP, located on both sides of the duplicated region. The reciprocal product of this recombination is a deletion of the same region, which is associated with hereditary neuropathy with liability to pressure palsies (HNPP; OMIM162.500). Proximal and distal CMT1A-REP sequences can be distinguished by the presence of a variant EcoRI site. We quantified the number of these repeat sequences in 36 CMT1A and 40 HNPP patients. CMT1A-REP sequences are involved in almost all of the mutations. The majority of recombination breakpoints occur distally from the variant EcoRI site. However, a few have a breakpoint proximal to this site, which creates the risk of misinterpretation with respect to a duplicated/deleted status.

Charcot-Marie-Tooth Disease↗
PubMed1996

[Melatonin: from hormone to drug?].

Melatonin is an indole hormone that is produced by the pineal gland, mainly at night, with a peak around 3.00 a.m. under normal environmental conditions. This endogenic secretion cycle is generated by the suprachiasmatic nuclei in response to the day/night alternation. Light either suppresses or entrains melatonin production according to the time of light exposure. Melatonin can be viewed as the "hand" of the internal clock and is regulated via the central nervous and sympathetic systems. Melatonin synchronizes biological cycles, particularly the temperature and sleep/wake cycles. Exogenous melatonin can influence the endogenous secretion of melatonin according to a phase response curve, an effect that provides a rationale for the use of melatonin to treat disorders of biological rhythms (rapid time-zone change syndrome, delayed sleep phase syndrome, desynchronization in blind subjects or shift workers, insomnia in the elderly). Other therapeutic indications are being considered (immune function disorders). Improvements in galenic forms (sustained-release presentations) or the development of analogs would be significant advances.

Body Temperature↗
PubMed1995

The effectiveness of combined oral lysine acetylsalicylate and metoclopramide compared with oral sumatriptan for migraine.

Aspirin is commonly used to treat migraine attacks, although sumatriptan, a much more expensive treatment, is also effective. We compared a combination of lysine acetylsalicylate (equivalent to 900 mg aspirin) and 10 mg metoclopramide (LAS+MTC) with oral sumatriptan (100 mg) and placebo in 421 patients with migraine. LAS+MTC was as effective as sumatriptan with a decrease of headache from severe or moderate to mild or none of 57% and 53%, respectively, for the first migraine attack treated. Both treatments were better than placebo (success rate 24%, p < 0.0001). LAS+MTC was significantly more effective in the treatment of nausea than sumatriptan (p < 0.0001) and was better tolerated (adverse events in 18% and 28%, respectively, p < 0.05). LAS+MTC is as effective as sumatriptan in the treatment of migraine attacks. It is also much cheaper.

Administration, Oral↗
PubMed1995

Magnetic resonance imaging evidence of decreased putamenal iron content in idiopathic Parkinson's disease.

OBJECTIVE: To determine the changes in basal ganglia iron content associated with various stages of idiopathic Parkinson's disease. DESIGN: Prospective magnetic resonance imaging study using a 2-T magnet. SETTING: Ambulatory care referral center. PATIENTS AND PARTICIPANTS: Forty-five patients suffering from levodopa-responsive Parkinson's disease and 45 age-matched controls. MAIN OUTCOME MEASURES: The T2 relaxation time calculated in various regions of the basal ganglia, the duration of Parkinson's disease, and the age of subjects. RESULTS: Patients with Parkinson's disease exhibited significantly decreased T2 relaxation time in the pars compacta of the substantia nigra compared with controls (P < .01), regardless of disease duration. Patients with a duration of illness above 10 years (n = 12) exhibited significantly increased T2 relaxation time in the anterior and posterior putamen (P < .005 and P < .01, respectively) and in the pallidum (P < .05) compared with age-matched controls. Putamental T2 relaxation time positively correlated with disease duration (P < .05). CONCLUSION: These results suggest that more complex brain iron changes than those previously reported are associated with idiopathic Parkinson's disease, including increased nigral iron content and decreased putamenal and pallidal iron concentration in patients with a duration of illness above 10 years.

Adult↗
PubMed1995

Mutations in the myelin protein zero gene associated with Charcot-Marie-Tooth disease type 1B.

Charcot-Marie-Tooth type 1 (CMT1) disease is an autosomal dominant neuropathy of the peripheral nerve. The majority of CMT 1 cases are due to a duplication of an 1.5-Mb DNA fragment on chromosome 17p11.2 (CMT 1a). Micromutations were found in the gene for peripheral myelin protein 22 (PMP22) located in the duplicated region of CMT 1a, and in the peripheral myelin protein zero (PO) located on chromosome 1q21-q23 (CMT 1b). We have characterized two new mutations in the PO gene in two french families presenting CMT disease. Both mutations occur in the extracellular domain of the PO protein. One mutation is a de novo mutation and is from paternal origin.

Base Sequence↗
PubMed1995

Restriction polymorphisms of the ceruloplasmin gene on chromosome 3.

Using a probe isolated from a human liver cDNA library, polymorphisms were observed in the human ceruloplasmin gene with the enzymes PstI and MspI. The PstI polymorphism was frequent (allele frequencies, 0.46 and 0.54) whereas the polymorphisms found with MspI were rare.

Ceruloplasmin↗
PubMed1995

Motor imagery of a lateralized sequential task is asymmetrically slowed in hemi-Parkinson's patients.

We examined seven right-handed, asymmetrical (right side affected) Parkinson's disease patients and seven age-matched controls in a manual finger sequencing test using left and right hands in vision, no vision, and motor imagery conditions. All patients displayed motor asymmetry, favoring the left hand. They also displayed motor imagery asymmetry, mentally simulating movement more slowly with their right affected hand than with their left hand. Additionally, impairment in mental hand rotation correlated significantly with the imagery asymmetry. These data support two related hypotheses: (a) Motor sequence imagery and execution share common neural structures. (b) The frontostriatal system is among these shared structures.

Adult↗
PubMed1995

Apomorphine in patients with Parkinson's disease.

We present a review of the recent literature and personal experience with apomorphine in patients with Parkinson's disease. Apomorphine is a potent D1 and D2 dopaminergic agonist. It has a rapid and short duration effect after subcutaneous administration at doses ranging from 15 to 180 micrograms/kg. Plasma maximal concentration is reached in 8-16 minutes, with a plasma half life of 34-70 minutes. Bioavailability is close to 100%. Repeated injections in patients show post-stimulative hyposensitivity. Apomorphine test appears very useful for the differential diagnosis between idiopathic Parkinson's disease and other Parkinson plus syndromes, and as a predictive test for dopaminergic responsiveness. Appropriate doses are able to alleviate akinesia, rigidity and tremor. Recent therapeutic trials have demonstrated the high interest of intermittent multiple subcutaneous apomorphine injections to cut the "off" motor phases in fluctuating parkinsonian patients under chronic levodopa treatment. In some cases, continuous apomorphine subcutaneous infusion with a portable pump may be required, particularly when levodopa treatment is temporarily interrupted, as after abdominal surgery. During long-term treatment, the apomorphine dose able to relieve akinesia remains stable. Peripheral side effects such as nausea and hypotension may be prevented by the co-administration of domperidone, a peripheral dopaminergic antagonist. Cutaneous fibrous nodules and psychiatric symptoms may occur, but usually at high dosages with continuous infusion. Local allergic effects have limited the use of other routes of administration, such as intranasal, sublingual, and rectal routes. Apomorphine is also used as a pharmacological tool for clinical research with the aim of a better understanding of the pathophysiology of Parkinson's disease.

Antiparkinson Agents↗
PubMed1995

[Hereditary motor and sensory neuropathy of Charcot-Marie-Tooth disease].

Charcot-Marie-Tooth disease (Hereditary Motor and Sensory Neuropathy) sometimes begins during childhood and can lead to learning and/or orthopedic disabilities. Due to the genetic and clinical heterogeneity of the disease, the diagnosis is based on a familial study of clinical, electromyographic and pathological abnormalities. Two major types of Charcot-Marie-Tooth disease have been described. Type 1 is characterized by a decrease in nerve conduction velocities and by a peripheral nerve hypertrophy due to myelinic alterations, while type 2 is the consequence of axonal alterations. Although type 1 and type 2 patients share similar clinical symptoms, type 2 patients have normal nerve conduction velocities and histological signs of axonal damage. Several genes involved in this disease have been recently located, and, in certain cases, an individual and direct diagnosis is available if the familial abnormality is related to chromosome 17.

Adolescent↗
PubMed1995

[Melatonin in humans: a biochemical marker of the circadian clock and an endogenous synchronizer].

Melatonin (MLT) is a methoxyindole secreted principally by the pineal gland. It is synthesized at night under normal environmental conditions. The endogenous rhythm of secretion is generated by the suprachiasmatic nuclei and activated by the light/dark cycle. Light is able to both suppress or activate melatonin production on the light schedule. The nycthohemeral rhythm of this hormone can be determined by repeated measurements of plasma or saliva MLT or urine sulfatoxy-MLT, the main hepatic metabolite. Melatonin can be considered as the output (the hand) of the endogenous clock. Since the regulating system follows a central and sympathetic nervous pathway, an abnormality at any level could unspecifically modify the MLT secretion, especially in patients with sympathalgia or dysautonomia. Melatonin plays the role of an endogenous zeitgeber on core temperature or sleep-wake cycle. Exogenous MLT is able to influence the endogenous secretion of the hormone according to a phase response curve. There are practical implications for this property in situations when biological rhythms are disturbed (jet-lag syndrome, delayed sleep phase syndrome, insomnia in blind people, shift-work, insomnia in elderly people). Improvement of pharmaceutical forms (controlled release preparations) or development of MLT analogs could lead to decisive progress.

Biomarkers↗
PubMed1995

Nocturnal melatonin excretion is decreased in patients with migraine without aura attacks associated with menses.

Nocturnal melatonin excretion was studied throughout a complete menstrual cycle in 10 women with migraine without aura attacks associated with menses and 9 women controls. Urine melatonin was determined by radioimmunoassay. The mean nocturnal melatonin excretion throughout the cycle was significantly lower in the migraine patients than in controls. In the control group, melatonin excretion increased significantly from the follicular to the luteal phase, whereas no difference was observed in the migraine group. Results are discussed in view of the role of the pineal gland in the organization of biological rhythms and homeostasis in relation to environmental conditions.

Adult↗