Osamu Yahara

TDP-43 pathology in sporadic ALS occurs in motor neurons lacking the RNA editing enzyme ADAR2

Both the appearance of cytoplasmic inclusions containing phosphorylated TAR DNA-binding protein (TDP-43) and inefficient RNA editing at the GluR2 Q/R site are molecular abnormalities observed specifically in motor neurons of patients with sporadic amyotrophic lateral sclerosis (ALS). The purpose of this study is to determine whether a link exists between these two specific molecular changes in ALS spinal motor neurons. We immunohistochemically examined the expression of adenosine deaminase acting on RNA 2 (ADAR2), the enzyme that specifically catalyzes GluR2 Q/R site-editing, and the expression of phosphorylated and non-phosphorylated TDP-43 in the spinal motor neurons of patients with sporadic ALS. We found that all motor neurons were ADAR2-positive in the control cases, whereas more than half of them were ADAR2-negative in the ALS cases. All ADAR2-negative neurons had cytoplasmic inclusions that were immunoreactive to phosphorylated TDP-43, but lacked non-phosphorylated TDP-43 in the nucleus. Our results suggest a molecular link between reduced ADAR2 activity and TDP-43 pathology.

Myotonic dystrophy type 2 in Japan: ancestral origin distinct from Caucasian families

Myotonic dystrophy type 2 (DM2) is caused by expansion of a tetranucleotide CCTG repeat in intron 1 of the ZNF9 gene on chromosome 3q21. All studied DM2 mutations have been reported in Caucasians and share an identical haplotype, suggesting a common founder. We identified a Japanese patient with DM2 and showed that the affected haplotype is distinct from the previously identified DM2 haplotype shared among Caucasians. These data strongly suggest that DM2 expansion mutations originate from separate founders in Europe and Japan and are more widely distributed than previously recognized.

Effect of xamoterol in Shy-Drager syndrome.

BackgroundXamoterol, a cardioselective β1-adrenoceptor partial agonist, has been reported to be effective on postural hypotension. We investigated the effect of xamoterol in five patients with Shy-Drager syndrome (SDS) in relation to their prevailing sympathetic nerve activity and sensitivity of β-adrenoceptors and the change in circadian variation of blood pressure. Methods and ResultsAmbulatory blood pressure over 24 hours was monitored by noninvasive sphygmomanometer (model 5200, Spacelab). Plasma norepinephrine levels of SDS patients were significantly lower than that of normal subjects (n=5) both at rest (54±15 versus 178±83 pg/ml) and after 10-minute standing (74±24 versus 318±143 pg/ml). Infusion of isoproterenol (0.02 μg/kg/min) produced a mild rise of systolic blood pressure and tachycardia in normal subjects but resulted in marked hypotension and tachycardia in SDS subjects. After xamoterol administration (200 mg b.i.d.), systolic blood pressure and heart rate were significantly increased in the averages during the day; however, increases were more pronounced at night. In two of the five patients, the improvement in dizziness was large enough to enable them to increase their daily activities. ConclusionsOur observations suggest that 1) β1-selective, high intrinsic sympathomimetic activity of xamoterol increases blood pressure and heart rate in patients with SDS as a consequence of their prevailing β1-adrenoceptor hypersensitive state, and 2) blood pressure monitoring over 24 hours appears to have important advantages in evaluating the therapeutic effects on postural hypotension.

Hypoxic ventilatory depression in a patient with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes

We describe a case of a 21‐year‐old man with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke‐like episodes (MELAS) who presented with hypoxic ventilatory depression. He had chronic hypoventilation, which was not explained by weakness of respiratory muscles. His hypercapnic ventilatory response was not impaired. In contrast, hypoxic ventilatory depression was observed in the isocapnic progressive hypoxic response test. After exposure to hypoxic conditions, his respiratory frequency decreased and tidal volume was unchanged. The hypoxic ventilatory depression was partially blocked by pretreatment with aminophylline. In conclusion, we need to be careful with patients with MELAS who are hypoxaemic because a vicious circle of hypoxia and hypoventilation can occur.

A Sporadic Case of Fabry Disease Involving Repeated Fever, Psychiatric Symptoms, Headache, and Ischemic Stroke in an Adult Japanese Woman.

Fabry disease can cause various neurological manifestations. We describe the case of a Japanese woman with Fabry disease who presented with ischemic stroke, aseptic meningitis, and psychiatric symptoms. The patient had a mutation in intron 4 of her α-galactosidase A gene, which was not detected in her family. This case suggests that Fabry disease should be considered in young patients who exhibit central nervous system symptoms such as ischemic stroke, even if there is no family history of the condition. The episodes of aseptic meningitis and stroke experienced by our patient suggest that persistent inflammation might be the mechanism underlying Fabry disease.