Annals of the New York Academy of Sciences
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Ann. N. Y. Acad. Sci. · Oct 2003
GABAergic neurons in the rostral mesencephalon of the macaque monkey that control vertical eye movements.
The mesencephalic reticular formation is important for the generation of vertical eye movements, but up until now the location of inhibitory premotor neurons is not known in primates. With tract-tracer methods combined with immunocytochemistry or in situ hybridization, we investigated the location of GABAergic premotor neurons in the rostral interstitial nucleus of the medial longitudinal fascicle (riMLF) and interstitial nucleus of Cajal (iC) in macaque monkeys. ⋯ However, in the iC, medium-sized and large GABAergic neurons were identified projecting contralaterally to the SO and IR motoneurons, and presumably the iC of the other side. These commissural GABAergic projections are well suited to inhibit the SO and IR motoneurons and possibly premotor down-burst-tonic neurons during upward eye movements.
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Ann. N. Y. Acad. Sci. · Sep 2003
ReviewCongenital myasthenic syndromes: multiple molecular targets at the neuromuscular junction.
Congenital myasthenic syndromes (CMS) stem from defects in presynaptic, synaptic, and postsynaptic proteins. The presynaptic CMS are associated with defects that curtail the evoked release of acetylcholine (ACh) quanta or ACh resynthesis. Defects in ACh resynthesis have now been traced to mutations in choline acetyltransferase. ⋯ The kinetic mutations increase or decrease the synaptic response to ACh and result in slow- and fast-channel syndromes, respectively. Most low-expressor mutations reside in the AChR epsilon subunit and are partially compensated by residual expression of the fetal-type gamma subunit. In a subset of CMS patients, endplate AChR deficiency is caused by mutations in rapsyn, a molecule that plays a critical role in concentrating AChR in the postsynaptic membrane.
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Ann. N. Y. Acad. Sci. · Sep 2003
ReviewMechanistic diversity underlying fast channel congenital myasthenic syndromes.
A host of missense mutations in muscle nicotinic receptor subunits have been identified as the cause of congenital myasthenic syndromes (CMS). Two classes of CMS phenotypes have been identified: slow channel myasthenic syndromes (SCCMSs) and fast channel myasthenic syndromes (FCCMSs). ⋯ This seemingly rare scenario has arisen with surprisingly high incidence over the past few years, and analyses of the syndromes have revealed a diverse array of mechanisms underlying the pathology. This review focuses on new mechanisms underlying the FCCMS.
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Valid and reliable measurements of muscle impairment are needed to assess therapeutic efficacy in patients with generalized myasthenia gravis. Several muscle scoring systems have been proposed for assessing muscle strength in such patients. The aim of the present study is to assess the validity and interobserver agreement of these muscle scores.
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Ann. N. Y. Acad. Sci. · Jun 2003
"Candidatus Rickettsia tarasevichiae" in Ixodes persulcatus ticks collected in Russia.
We collected 209 Ixodes persulcatus ticks in various regions of Russia, including the southern Urals and western and eastern Siberia. Using PCR amplification and sequencing of the citrate synthase-encoding gene (gltA), we detected a new rickettsial genotype, which we named "Candidatus Rickettsia tarasevichiae." This bacterium was found in 9.27%, 10.0%, and 20.5% of the ticks collected in western Siberia, eastern Siberia, and the southern Urals, respectively. "Candidatus Rickettsia tarasevichiae" exhibited a 98% and 96% nucleotide sequence homology, with the 16S rDNA and gltA sequence, respectively, of R. canadensis, a rickettsia previously only found in Haemaphysalis leporispalustris ticks in North America. The phylogenetic analysis of "Candidatus Rickettsia tarasevichiae" and other Rickettsia species allowed the creation of a new cluster with high bootstrap values within the Rickettsia genus involving this rickettsia, R. canadensis, and three uncultured rickettsiae from plant insects.