Mapping of the human NMDA receptor subunit (NMDAR1) and the proposed NMDA receptor glutamate-binding subunit (NMDARA1) to chromosomes 9q34.3 and chromosome 8, respectively

A role for the N-methyl-D-aspartate (NMDA) receptor in the molecular pathology underlying Huntington disease (HD) has been proposed on the basis of neurochemical studies in HD and the ability of the NMDA receptor to mediate neuronal cell death. The molecular cloning of the human NMDA receptor subunit (NMDAR1) and a proposed glutamate-binding subunit of the NMDA receptor (NMDARA1) have provided an opportunity to test the hypothesis that either of these genes might be directly involved in the causation of HD. We have mapped NMDAR1 to 9q34.3 using in situ hybridization studies and NMDARA1 to human chromosome 8 using a somatic cell hybrid panel. Because the gene causing HD has been localized to chromosome 4p16.3, the chromosome assignments reported here are inconsistent with either of these genes playing a causative role in the molecular pathology of HD. However, it is noteworthy that the gene for torsion dystonia has also been localized by genetic studies to 9q34.3, the same regional map location as NMDAR1.

NMDA treatment and K(+)-induced depolarization selectively promote the expression of an NMDA-preferring class of the ionotropic glutamate receptors in cerebellar granule neurones

Growth conditions which promote the survival of cerebellar granule cells in culture, such as high K+ or N-methyl-D-aspartate (NMDA) treatment, also promote the functional expression of an NMDA-preferring subtype alone of the ionotropic glutamate receptors. The selective regulation of NMDA receptors detected electrophysiologically in individual cells, using the whole cell patch clamp technique, is characteristic of granule cells in general: NMDA-induced 45Ca2+ influx increased several-fold in cultures treated with either high K+ or NMDA. The increase in NMDA receptor activity was correlated with an increase in the expression of an NMDA receptor protein. Since the effect of these 'trophic' conditions is mediated through Ca2+, the induced increase in the density of NMDA receptors (which gate a Ca2+ conductance) provides a positive feedback for strengthening the trophic influences.

Antioxidants prevent the interaction of 3,4-dihydroxyphenylacetic acid at the dopamine D2 receptor

Antioxidants such as ascorbic acid (AA) and dithiothreitol (DTT), can prevent 3,4-dihydroxyphenylacetic acid (DOPAC) inhibition of [3H]spiperone binding to neuronal dopamine D2 receptors. The DOPAC quinone produced from auto-oxidation is believed to be responsible for the irreversible inhibition noted. Quinone conjugation to proteins occurs readily in vivo, and thus, auto-oxidation of DOPAC and other endogenous catechol containing compounds could be an important component of protein modification during on-going neuronal physiology.

Effects of anti-glutamate-binding protein antibodies on synaptic membrane ion flux, glutamate transport and release, and L-glutamate binding activities

Antibodies (Abs) raised against the L-glutamate-binding protein (GBP) purified from bovine brain were used to define the possible physiologic activity of GBP in synaptic membranes. Three processes were examined for their sensitivity to the Abs: the excitatory amino acid stimulation of thiocyanate (SCN-) flux, the transport of L-glutamic acid across the synaptic membrane, and the depolarization-induced release of L-glutamate. Only the amino acid-induced changes in ion flux were inhibited by the anti-GBP Abs. The change in membrane potential produced by exposure of synaptic membranes to excitatory amino acids was measured as the increase in the uptake of the lipophilic anion SCN-. The L-glutamate-induced SCN- influx was 40 times more sensitive to inhibition by the anti-GBP Abs than the stimulation of ion flux by kainate, and 60 times more sensitive than that produced by quisqualate. The anti-GBP Abs did not inhibit the activation of ion flux produced by N-methyl-D-aspartate. The inhibition of glutamate-stimulated ion fluxes by the Abs was complete, whereas the inhibition of L-glutamate binding to either the rat or bovine brain GBP was not. The results obtained indicated that although the majority of the anti-GBP Abs were not directed against the glutamate recognition site of the GBP and of presumed synaptic membrane receptors, they were effective in blocking the activation of receptor-associated ion channels. Thus, the GBP may be considered a component of some excitatory amino acid receptor complexes.

[An example of partnership cooperation. Cantonal League against Tuberculosis and Lung Diseases/Association "Das Band"]

Together with the Cantonal League against Tuberculosis and Lung Diseases of Zurich, the Association "Das Band" has organized a first course for parents of children with asthma. The course is a component of the associations new "Prophylaxis Program for Children with Asthma and Their Parents". By exchanging ideas, the parents should become able to reflect their situation, characterized by excessive protectionism, aggressiveness, and guiltiness, and they also should learn to accept the disease as a part of their daily life. The first course, which meanwhile is followed by a second one, provided a first base for the solution of the many problems.

[Centronuclear myopathy with autosomal dominant inheritance(author's transl)]

For the first time in Germany cases of a "centronuclear myopathy" are described in a 14-year-old boy and his 18-year-old sister. First symptoms in both patients appeared at 4 to 5 years of age with a "sleepy facial expression", clumsy gait and rapid fatigue. Within few years the disease progressed to generalized muscle weakness and atrophy, ptosis, ophthalmoplegia externa and areflexia. Weakness and atrophy were most pronounced in the distal muscles of the lower extremities. Both patients were free of epilepsy and the EEG recordings were normal. Motor and sensory nerve conduction velocities were normal. Repetitive stimulation of nerves revealed a normal transmission from nerve to muscle. Muscle biopsy showed a type I muscle fiber hypotrophy and a type II muscle fibre hypertrophy in addition to a predominance of type I fibres. Both fibre types showed central nuclei, sometimes appearing as chains in longitudinal sections. In most cells with central nuclei there persists a very small pericentral zone free of myofibrils but with increased activity of oxidative enzymes and phosphorylase. 2--3% of muscle fibres in cross sections showed a decreased of absent enzyme activity in the most peripheral fibre zone. Electron microscopy showed evidence of a centrally distinct myofibrillar disintegration. The father of both children had a ptosis at least from the 20th year of age. 5 years later generalized progressive muscle atrophy was recorded. Aged 51 years he died of pneumonia. Though not proved most probably the father suffered from the same disease as the children, pointing to an autosomal dominant inheritance in this family. The disease, according to the literature, seems to be genetically heterogeneous. The clinical picture seems to be independent of the mode of inheritance. Our patients showed a relatively rapid progression of symptoms. Pathogenetically the "centronuclear myopathy" may result from a disturbance of correlated nerve-muscle structures starting during early fetal life.