[Progressive muscle atrophy. A rarely diagnosed variant of amyotrophic lateral sclerosis]

Progressive muscle atrophy (PMA) is a degenerative disease of the lower motor neuron. The course of the illness and the fatal prognosis correspond to those of amyotrophic lateral sclerosis (ALS). Neuropathologic and genetic findings support categorizing PMA within the spectrum of ALS, even though no clinical sign of a disorder of the upper motor neuron is demonstrable. The diagnosis of PMA is based on advanced extremity pareses and atrophies with a high progression rate. Respiratory insufficiency is determinative of the prognosis. Absent or late affection of bulbar functions is characteristic of the disease. Intraneuronal bunina bodies and ubiquitine-positive inclusions, which are established morphologic characteristics of ALS, are found post mortem. The treatment options of riluzol medication, respiratory therapy, and nutrition are analogous to those for typical ALS.

The p150 subunit of dynactin (DCTN1) gene in multiple sclerosis

OBJECTIVES

Mutations in the p150 subunit of the axonal transport protein dynactin (DCTN1) have been reported in patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Given the common features of neurodegeneration in multiple sclerosis (MS), FTD and ALS, sequence variants of the DCTN1 gene may be a contributory factor to neurodegeneration in MS.

METHODS

We investigated a total of 200 MS patients and 200 controls. A total of 100 patients had a relapsing-remitting form of MS, 100 cases were primary progressive. Sequence alterations were screened for in the coding region of DCTN1 using heteroduplex and sequence analyses.

RESULTS

Two heterozygous missense mutations (T1249I, I196V) were found in two healthy control subjects. No mutations were identified in 200 MS patients. The frequency of a known single nucleotide polymorphism (R495Q) was not significantly different between patients and controls.

CONCLUSION

The results indicate that the DCTN1 gene is probably not influencing susceptibility to neurodegeneration in MS.

Early-onset ALS with long-term survival associated with spastin gene mutation

The authors report a 73-year-old patient with a natural history of early-onset ALS for 49 years presenting with limb and bulbar amyotrophy and a pyramidal syndrome. Analysis of the locus SPG4 identified a heterozygous duplication mutation (c.304_309dupGCCTCG) within exon 1 of the spastin gene. We propose that sequence alterations of spastin may comprise a genetic risk factor in a greater spectrum of motor neuron disorders including clinical variants of ALS.

Reactive astrocytes and macrophages in the brain stem of SIDS victims? Eleven age- and sex-matched SIDS and control cases

The investigation was carried out on 11 sudden infant death (SIDS) cases which were compared with age- and sex-matched controls. Six brain nuclei were selected for evaluation. Using immunohistochemical methods, macrophages were selectively demonstrated by detection of lysozyme; reactive astrocytes, by detection of intracytoplasmic albumin (marker of prior impairment of blood-brain barrier function) or GFAP. No lysozyme-positive cells were demonstrable in the brain stem of any of the examined cases. Although a greater number of reactive, GFAP-expressing astrocytes were found in the SIDS cases, 3 of the 11 SIDS cases (compared to 5 controls) had no reactive astrocytes in any of examined brain nuclei. Reactive astrocytes, however, were identified in more than half the controls. Sections treated with anti-albumin serum were evaluated quantitatively. Total number of non-neuronal cells, relative proportion of astrocytes, and proportion of albumin-positive astrocytes were determined. Paired brain nuclei were counted on both sides of the brain stem. The number of non-neuronal cells, astrocytes, and albumin-positive astrocytes in the SIDS cases did not differ significantly from those in the controls. No statistically relevant difference was established between the right and left parts of the brain stem. The findings were discussed in light of the literature.

Dimeric ubiquinol:cytochrome c reductase of Neurospora mitochondria contains one cooperative ubiquinone-reduction centre

Dimeric ubiquinol:cytochrome c reductase of Neurospora mitochondria was isolated as a protein-Triton complex and free of ubiquinol (Q). The enzyme was incorporated into phosphatidylcholine membranes together with Q. The effects of varying the molar ratio of Q to enzyme on the electron transfer from duroquinol (DHQ2) to the cytochromes c, c1 and b were studied. The rate of electron flow from DQH2 to cytochrome c was 15 times increased by Q and was maximal when one molecule of Q was bound to one enzyme dimer. The apparent Km value for DQH2 of the Q-free enzyme was 5 microM and of the Q-supplemented enzyme 25 microM. The pre-steady-state rate of electron transfer from DQH2 to cytochrome c1 was also 15 times increased by Q and was maximal with one Q molecule bound to one enzyme dimer. This effect of Q was inhibited by antimycin. The pre-steady-state rate of electron transfer from DQH2 to cytochrome b was 5 times decreased when Q was bound to the enzyme and this effect of Q was insensitive to myxothiazol. The H+/2e- stoichiometry with DQH2 as substrate of the Q-supplemented enzyme was 3.6. These results are interpreted in accordance with a Q-cycle mechanism operating in a dimeric cytochrome reductase. Each enzyme monomer catalyses a single electron transfer from the QH2-oxidation centre to the Q-reduction centre and the two monomers cooperate in the reduction of Q to QH2 at one Q-reduction centre. This centre contains two different binding sites for Q. DQH2 does not properly react at the QH2-oxidation centre. DQH2, however, binds to the loose Q-binding site of the Q-reduction centre and reduces the Q bound to the tight Q-binding site of the centre. The QH2 thus formed at the Q-reduction centre serves as electron donor for the QH2-oxidation centre.