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V Ramaekers

Publications and source records attributed to V Ramaekers.

10 recordsLinked to original sources
PubMed2000

Non-invasive approach of motor unit recording during muscle contractions in humans.

Information about the structural and functional characteristics of the motor unit (MU) is highly relevant for the diagnosis of neuromuscular disorders. Electromyography (EMG) is a suitable method for obtaining the information needed. The problem is the separation of the activity of one MU from others which are simultaneously active. Such investigations of single MU activity have commonly used invasive methods, e.g. employing a needle or a wire. Conventional surface-EMG methods have limited resolution and detect, at high contraction levels, multiple MU superimposed one on the other. The separation of the activity of a single MU can be achieved in a non-invasive way when highly specialised acquisition techniques are used. One approach, called high spatial resolution EMG (HSR-EMG), is based on the use of multi-electrode arrays in combination with a two-dimensional Laplace filter. The HSR-EMG permits the completely non-invasive detection of single MU activity even during maximal voluntary contractions. First applications have shown that the method provides a deeper insight into the functional and structural characteristics of the MU. In this paper the application of HSR-EMG to the diagnosis of neuromuscular disorders will be presented, and the latest results will be given of its application in the evaluation of treatment of patients with plexus lesion.

Electromyography↗
PubMed1999

A common mutation (epsilon1267delG) in congenital myasthenic patients of Gypsy ethnic origin.

OBJECTIVE: Mutation analysis of the acetylcholine receptor (AChR) epsilon subunit gene in patients with sporadic or autosomal recessive congenital myasthenic syndromes (CMS). BACKGROUND: The nicotinic AChR of skeletal muscle is a neurotransmitter-gated ion channel that mediates synaptic transmission at the vertebrate neuromuscular junction. Mutations in its gene may cause congenital myasthenic syndromes. A recently described mutation in exon 12 of the AChR epsilon subunit (epsilon1267delG) disrupts the cytoplasmic loop and the fourth transmembrane region (M4) of the AChR epsilon subunit. METHODS: Forty-three CMS patients from 35 nonrelated families were clinically classified as sporadic cases of CMS (group III according to European Neuromuscular Centre consensus) and were analyzed for epsilon1267delG by PCR amplification and sequence analysis. RESULTS: The authors report the complete genomic sequence and organization of the gene coding for the epsilon subunit of the human AChR (accession number AF105999). Homozygous epsilon1267delG was identified in 13 CMS patients from 11 independent families. All epsilon1267delG families were of Gypsy or southeastern European origin. Genotype analysis indicated that they derive from a common ancestor (founder) causing CMS in the southeastern European Gypsy population. Phenotype analysis revealed a uniform pattern of clinical features including bilateral ptosis and mild to moderate fatigable weakness of ocular, facial, bulbar, and limb muscles. CONCLUSIONS: The mutation epsilon1267delG might be frequent in European congenital myasthenic syndrome patients of Gypsy ethnic origin. In general, patients (epsilon1267delG) were characterized by the onset of symptoms in early infancy, the presence of ophthalmoparesis, positive response to anticholinesterase treatment, and the benign natural course of the disease.

Adolescent↗
PubMed1999

Persistent hyperplastic primary vitreous: MRI.

Persistent hyperplastic primary vitreous (PHPV), a developmental cause of leukocoria, is due to incomplete regression of the fetal blood supply to the eye. We report the MRI features of PHPV of the dorsal type to facilitate differential diagnosis from other causes of leukocoria, namely retinoblastoma, which may have major therapeutic consequences.

Child↗
PubMed1996

Mutation analysis of the pyruvate dehydrogenase E1 alpha gene in eight patients with a pyruvate dehydrogenase complex deficiency.

Most of the mutations causing deficiency of the pyruvate dehydrogenase (PDH) complex are in the X-linked E1 alpha gene. We have developed a rapid screening method for the detection of mutations in this gene using reverse transcription of total RNA, polymerase chain reaction amplification of the whole coding region of the gene and single-strand conformation polymorphism (SSCP) analysis. With this method, we studied eight patients with a PDH complex deficiency, using cultured fibroblasts. In all patients, aberrant SSCP patterns were found and, after sequencing of the corresponding fragments, we were able to identify six new mutations and two mutations already described previously. The mutations are point mutations leading to amino acid substitutions (5) and direct repeat insertions (3). The presence of the mutations was confirmed in genomic fibroblast DNA. The 4 female patients were shown to carry both a normal and a mutated E1 alpha gene.

Base Sequence↗
PubMed1993

[Suprasellar space-occupying lesion as initial manifestation of tuberculosis in childhood].

Three days after having sustained a mild trauma to the head a seven-year-old boy developed seizure-like rotatory vertigo. Computed tomography, magnetic resonance imaging and cerebral angiography demonstrated a suprasellar space-occupying lesion. Pulmonary tuberculosis was discovered in subsequent diagnostic work-up. Cerebrospinal fluid examination was unremarkable except for immunological tests (tuberculostearic acid) which pointed to central nervous system (CNS) involvement so that a tuberculoma was suspected. The lesion decreased in size on tuberculostatic treatment (200 mg/d isoniazid, 200 mg/d rifampicin, two times 250 mg/d pyrazinamide). In the next 12 months there merely persisted a mild abnormality of the blood-brain barrier with a little contrast-medium uptake, which regressed in the following 6 months. The differential diagnosis between CNS tuberculosis and brain tumour or pyogenic abscess can be difficult in children if there are no pulmonary signs and/or the cerebrospinal fluid is normal.

Antitubercular Agents↗
PubMed1993

Subtotal aplasia of myelinated nerve fibers in the sural nerve.

Thus far, only very few cases with neuronal maldevelopment in the peripheral nervous system have been reported (Table 1). The present sporadic case manifested itself with peripheral sensorimotor polyneuropathy in early infancy. Clinical findings included pareses and hypaesthesia of distal extremities and severely reduced nerve conduction velocities. During adolescence, cerebellar ataxia developed. Sural nerve biopsy taken at the age of 14.5 years showed severe fascicular hypoplasia, aplasia of large myelinated nerve fibers, and subtotal deficiency of small myelinated nerve fibers without numerical reduction of unmyelinated axons. There was no structural evidence of a progression of myelinated fiber breakdown although some collagen pockets and empty Schwann cell processes among preserved unmyelinated axons indicated some loss of unmyelinated fibers. These findings are interpreted as representing maldevelopment of the myelinated fibers in the peripheral nervous system. Appropriate classification of this unique disease among the known developmental disorders of peripheral nerves is discussed.

Adolescent↗
PubMed1993

A novel mutation in the proteolipid protein gene leading to Pelizaeus-Merzbacher disease.

Point mutations of the gene of human proteolipid protein (PLP) have been recognized as the molecular basis of one form of leukodystrophy, the X-chromosome-linked Pelizaeus-Merzbacher disease (PMD). We report the molecular analysis of four PMD patients in three unrelated families and describe a point mutation (G-->A transition) in exon V which leads to the substitution of Gly216 by a serine residue in a highly conserved extracytosolic domain and a Mae I RFLP. Molecular modelling with energy minimization indicates that this seemingly minor alteration of the amino-acid sequence induces a considerable conformational change and tight packing of the polypeptide chain apparently not compatible with the regular PLP function in oligodendrocytes. This mutation has been detected and characterized by PCR amplification of genomic DNA using intron and exon primers and the complete sequence analysis of the seven exons and a 300 bp promoter region of the PLP gene of two affected brothers. The sequence analysis of a PCR fragment representing exon V amplified from genomic DNA of different kindreds of the pedigree revealed the mother as the only carrier indicating that the mutation has occurred de novo in the mother's germline. PLP gene (including the 8.8 kb intron I) rearrangements have been excluded by Southern blot hybridization and overlapping PCR amplification of genomic DNA.

Base Sequence↗
PubMed1988

Feeding, behavioural state and cardiorespiratory control.

The aim of the present study was to examine whether immaturity of cardiorespiratory control corresponds to a less mature behavioural state pattern and/or to less efficient feeding behaviour. Fifty-four infants were observed and data polygraphically recorded for 6 hours; a feeding session was included. It was found that infants with immature cardiorespiratory control spent more time in REM-sleep, less time in the active awake state, and were more likely to be inefficient feeders. In addition, 100 infants were observed for risk signs of sudden infant death syndrome and their parents were asked to answer a questionnaire on the sleeping and feeding behaviour of their infants. The majority of the infants with immature cardiorespiratory control were described as bad feeders but good sleepers. We conclude that gathering information about sleeping and feeding behaviour is useful when screening for immaturity of cardiorespiratory control.

Apnea↗