Myasthenia gravis in Jamaica: clinical, immunological and genetic studies

Clinical, immunological and genetic parameters were studied in 73 Jamaican patients with myasthenia gravis (Mg). The reported biomodal clinical distribution of females with early onset of disease and males with late onset was not observed. The female to male ratio was 2:1. The most frequent manifestations of disease were ptosis (84.9 percent), general muscle weakness (68.5 percent), bulbar symptoms (41.1 percent) and diplopia (32.9 percent). Unusual presenting features such as unilateral ptosis, recurrent chest infection and stumbling while walking resulted in diagnosis being missed in 5.8 percent of cases. The sensitivity of radiommunoassay in detecting acetylcholine receptor antibody (AchR-Ab) in sera from a subgroup of 35 MG patients was 71.4 percent whilst that of the ELISA was only 14.2 percent. There was no correlation between HLA-type, thymic pathology and course of disease. HTLV-I could not be implicated in the pathogenesis of this disease. There was a paucity of other associated autoimmune conditions among MG patients. Thymectomy was an important therapeutic modality in that improvement was observered in 22 cases and remission in 11. (AU)

Central cholinergic involvement in the mediation of spontaneous motor activity in rats

Spontaneous motor activity of preweanling rats (14-day-old) was examined in an activity cage following the administration of atropine at 1.0, 2.5, 5.0, and 10.0 mg/kg respectively. Compared with saline-control animals, atropine at these dosages, did not significantly affect the activity level of the 14-day-old rat. The motor activity of 14-20-day-old rats was also measured following the administration of atropine (10mg/kg) in the Y-maze and the activity cage. The activity level was significantly decreased in (a) all ages in Y-maze and (b) the 18-day-old animals only in the activity cage. In contrast, amphetamine (2.0, 4.0, and 10.0 mg/kg) induced significant increments in spontaneous motor activity. It is suggested that a cholinergic mechanism concerned with the modulation of central nervous system arousability becomes functional at 18 days of age, that is, subsequent to a more caudal arousal inducing mechanism, which seems to be mediated by a catecholaminergic system (AU)