Biomedical subjects
Publications and source records attributed to J Pouget.
After a review of the metabolism and pharmacology of adenosine, this work will examine the various therapeutic possibilities involving the use of agonists or antagonists of adenosine A1 or A2 receptors in neurological disorders. Promising preclinical results have been obtained with epilepsy, cerebral ischemia, alcoholism, and pain.
Chronic hepatitis C virus (HCV) infections are often associated with extrahepatic immunological manifestations, including various autoimmune disorders. The aims of this study were to determine the prevalence of HCV markers in patients with myasthenia gravis (MG) and to determine any relationship with HCV infection. Eighty-three patients with MG. 40 men aged 20-93 years and 43 women aged 13-87 years (mean age 54 years) were studied. The MG patients were positive for antibody to acetylcholine receptor in addition, their sera was analysed for antibody to HCV (HCVAb) and HCV RNA, HCVAb was detected in two of the 83 patients (2.4%). Four patients were repeatedly HCV RNA positive. They were infected by HCV genotype 1 (one patient), HCV genotype 2a (two patients) and an undetermined HCV genotype in one patient. They received plasmapheresis or intravenous immunoglobulin treatment. Among the four patients, one was infected after the onset of MG without receiving a blood transfusion or using intravenous drugs. The other three had chronic hepatitis C which was discovered at the same time as MG and only one patient had been exposed to blood products. The prevalence of HCV markers in patients with MG (4.8%) was higher than that reported for the general French population, about 1%. This prevalence is similar to that occurring in patients exposed to plasmapheresis or intravenous immunoglobulin. In conclusion, HCV appears to play little, if any, role in causing MG. The higher prevalence of infection among MG patients may be related to transmission in the course of therapy.
Eight elderly patients developed progressive paravertebral muscle weakness with bent spine on standing but normal supine posture. Computed tomography showed pronounced hypodensity of the paraspinal muscles. Serum creatine kinase was moderately increased, paraspinal EMG non-specific, and biopsy myopathic. The syndrome was familial in two patients and may be caused by a late onset paraspinal muscle dystrophy. In the absence of specific pathological changes, such cases could be classified as having "bent spine syndrome".
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.
Gait analysis of 13 patients affected by Parkinson's disease (PD) and 7 healthy elderly volunteers was performed with a fully automatic motion analyser. The recording included stride parameters for walking velocity, stride length, stride duration and swing time. Maximal amplitudes of rotation of the hip, knee and ankle were also recorded. The analysis was performed for the PD's patients before and after L-Dopa intake. All the patients walked with and without transversal stripes on the floor. The contrasting white lines were 45 cm apart. After medication, the stride length, the velocity and the swing phase duration were significantly increased. The movements around the hip, knee and ankle joints that were initially reduced, poorly increased after L-Dopa intake. When stripes were placed on the floor, no significant changes occurred for the overall group of patients. Seven parkinsonian patients did improve with visual guidance, increasing their stride length and their speed. Some rotations of hip and knee were also influenced by stripes. This sub-group of patients was characterized by older age, a slower walking velocity, a smaller stride length and a shorter swing time. We correlated the sensitivity to visual cues to the defect of the visual contrast sensitivity that has been established in PD by several recent works. Locomotion on the transverse lines might have produced a motion perception at a rate determined by the speed of the patient. For appropriate intervals between stripes, one can hypothesise that the resulting visual stimuli belonged to a range of spatio-temporal frequencies that are decreased in patients with PD.
31-P MR spectroscopy has been used to investigate metabolic events surrounding muscular contraction in a patient with an unusual myopathy characterized by clinical signs of muscle stiffness and swelling after prolonged exercise. Histological assays demonstrated a predominance of type II fibers with tubular aggregates. These structures had low calcium content although calcium-ATPase protein was present. Metabolic measurements were normal at rest except for the presence of a marked signal in the phosphodiester region which could reflect membrane abnormalities. Exercise-induced PCr consumption was in the normal range but the extent of the related intracellular acidosis was abnormally large. Kinetics of PCr and PCr/Pi ratio post-exercise recovery were delayed, but were likely to reflect the effect of the very low end-of-exercise pH rather than an aerobic deficiency. Finally, proton efflux from muscle to bloodstream, measured during the initial recovery period, was delayed, indicating altered mechanisms of proton handling. The most prominent metabolic abnormality recorded is the large glycogenolysis-induced pH decrease which might be linked to either abnormal activation of glycogenolysis and/or impaired proton and lactate handling within the muscle. The association between tubular aggregates and hyperacidosis is of interest but the exact causal relationship remains to be elucidated.
Since the first cases described in 1986, multifocal motor neuropathy with persistent conduction blocks (MMN) appears to be a well-defined nosological entity. Clinical features include male-predominant occurrence, weakness often accompanied by cramps and fasciculations; topography of the motor involvement is characterized by assymetry, upper limb predominance, relation to the distribution of individual nerves or roots. Atrophy is variable but can lack despite severe weakness. Multifocal, purely motor and persistent conduction blocks are the electrophysiological hallmark of the disease. Serum antibodies against ganglioside GM1 are frequently associated with MMN but their diagnostic sensitibity and specificity are discussed. However high level of these antibodies may be a useful immunological marker of MMN. Their pathogenic role is probable, perhaps by their interaction with ionic channels localized in node of Ranvier. Morphological findings, immunologic abnormalities and improvement with intravenous immunoglobulin therapy define MMN as a type of inflammatory demyelinating neuropathy. Their relation with CIDP are discussed.
Multifocal motor neuropathy is characterized by a progressive asymetrical weakness, predominantly affecting the upper limbs with persistent conduction blocks on motor but not sensory nerves. Treatment woth prednisone and plasma exchanges have failed to demonstrate any positive effects. Some improvements have been reported with cyclophosphamide. Mainly immunoglobulin therapy has been evaluated with a beneficial response in almost 70% of the cases. These benefits obtained over periods of less than six months have recently been confirmed by a long-term evaluation of 18 patients treated by repeated infusions.
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Palmaris brevis spasm syndrome is a rare and benign condition of localised muscular hyperactivity. In five men, the hypothenar eminence underwent spontaneous, irregular, tonic contractions of the palmaris brevis muscle. An EMG showed spontaneous high frequency discharges of normal motor units, without evidence of neuropathy or of nerve compression. This syndrome resembles other restricted muscle hyperactivity syndromes although there are some differences. Curiously, the palmaris brevis muscle is not under voluntary control. The mechanism of the syndrome could be an ephaptic transmission possibly secondary to the transient and repeated stretching of the ulnar nerve superficial branch. In one patient a root compression was the probable origin.
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In primary fibromyalgia the main symptom is diffuse pain predominating at tender points which are sensitive to palpation. The aim of this study was to compare the effects on the amplitude of the nociceptive flexion reflex of the lower limb (RIII reflex) of applying painful pressure to the tender points with the effects of the same pressure applied to other points of the body or to the same part of the body in control subjects. This method was chosen because previous studies have shown that it was possible to activate the diffuse noxious inhibitory system using a "counter-irritation" stimulation. Our study was carried out on 18 fibromyalgic patients and on 12 control subjects. During the counter-irritation procedure, consisting of applying pressure with a mechanical dolorimeter to tender points, a clear cut and significant decrease in the amplitude of the RIII response was observed in 6 patients. In conclusion, in view of the subjective nature of the criteria used at present to diagnose primary fibromyalgia, we would like to suggest that a positive counter-irritation test be adopted as a further obligatory criterion, since it has been clearly established that the diffuse noxious inhibitory control responsible for the decrease in the RIII amplitude can be activated only when the subjects undergo intense nociceptive stimulation.
Painful legs and moving toes is a rare syndrome with controversial physiopathology. We report two cases that were relieved by applying transcutaneous vibratory simulation. The pain relief was objectively evaluated using the nociceptive flexion reflex of the lower limb (RIII reflex). In these patients, we found a deficiency in circulating adenosine levels, which was not found in other chronic painful syndromes (sciatic pain). Based on these observations, we successfully treated patients with painful legs and moving toes by the administration of ATP. The deficit in blood adenosine may be an explanation of the physiopathology of this syndrome.