Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aromatic and heterocyclic esters of 1-methyl-4-piperidinol and 1,4-dimethyl-4-piperidinol and aromatic esters of (dialkylamino)alkanols were prepared and evaluated for antiepileptic activity by the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole seizure threshold (scMet) assays and for minimal central neurotoxicity by the rotorod ataxia test. The most potent compound, namely the 2-phenylbenzoate (57) of 3-(diethylamino)propanol, was slightly more potent than diphenylhydantoin in the MES assay, while the 2-phenylbenzoate (24) of 1-methyl-4-piperidinol and the 2-phenylbenzoate (56) of (diethylamino)ethanol displayed activity comparable to that of diphenylhydantoin. The 2-phenethylbenzoate ester (6) of 1-methyl-4-piperidinol exhibited one-third the activity of diphenylhydantoin. The 2,4,5-trimethylbenzoate 40 and 2,4,6-trimethylbenzoate 41 of 1-methyl-4-pieridinol were even less potent, but did display activity in the phenobarbital-methsuximide range. Certain compounds interact with sites associated with the GABA receptor-chloride channel complex, but their potencies as anticonvulsant agents do not correlate with interaction at sites on the channel complex. Certain analogues antagonize binding of a batrachotoxin analogue to sodium channel sites, a property indicative of local anesthetic activity. There are structural similarities between 2-phenylbenzoates 57, 56, and 24 and diphenylhydantoin, and the latter anticonvulsant also antagonizes binding of the batrachotoxin analogue.
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PMID:Anticonvulsant activity of piperidinol and (dialkylamino)alkanol esters. 301 69

The symptoms of poisoning caused by pyrethroids are characterized by ataxia, loss of coordination, hyperexcitation, convulsions, and paralysis. Depending on the type of pyrethroid, repetitive discharges and/or conduction block are observed in various regions of the nervous system. Type I pyrethroids as represented by allethrin and tetramethrin which lack a cyano group cause repetitive discharges in nerve fibers and nerve terminals leading to hyperexcitation of the animal. Type II pyrethroids as represented by cyphenothrin, deltamethrin and fenvalerate which contain a cyano group at the alpha-carbon cause nerve membrane depolarization and block leading to paralysis of the animal. Both types of action are ascribed to modifications of nerve membrane sodium channels which result in very slow gating kinetics. Patch clamp single channel recording experiments have clearly demonstrated that individual sodium channels are modified by tetramethrin in an all-or-none manner to give rise to a prolonged opening without change in conductance. Thus, it is concluded that the site of action of pyrethroids is the sodium channel, and that pyrethroids interact with the channel macromolecules that control the gating mechanism.
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PMID:Cellular and molecular mechanisms of action of insecticides: neurophysiological approach. 630 35

Lamotrigine (LTG) inhibits repetitive high frequency firing in depolarised neurones by selectively prolonging slow inactivation of the sodium channel, thereby suppressing the release of excitatory amino acids. It has been shown to be effective in 11 pivotal double-blind add-on trials in patients with refractory partial seizures with or without secondary generalisation. Subsequent anecdotal data support its efficacy for typical and atypical absences, myoclonic jerks, tonic or clonic seizures, Lennox-Gastaut syndrome and infantile spasms. Most recently LTG has been compared with carbamazepine and phenytoin in double-blind trials in patients with newly diagnosed partial and primary and secondary generalised tonic-clonic seizures. At the doses used, its efficacy was similar to the older agents for all seizure types, but LTG was better tolerated than both of the older agents. The commonest side-effects with LTG include headache, nausea, diplopia, dizziness, ataxia and tremor. Rash occurs in fewer than 5% patients. Its incidence can be reduced by starting treatment with a low dose, particularly in patients receiving concomitant sodium valproate which inhibits LTG metabolism. Enzyme inducers, such as carbamazepine, phenytoin and phenobarbital, accelerate its elimination, but LTG itself has no effect on hepatic metabolic processes. A pharmacodynamic interaction with carbamazepine necessitates a dosage reduction in some patients when LTG is introduced. LTG is a new antiepileptic agent with a long elimination half-life, a broad spectrum of activity, and a wide therapeutic ratio.
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PMID:Lamotrigine--an update. 895 Dec 13

Recent advances in the field of molecular myology have provided significant insight into the pathological mechanisms underlying a variety of neuromuscular disorders. Genetic abnormalities can now be linked to primary and secondary pathophysiological changes in muscle fibres which compromise structural, metabolic, regulatory or contractile mechanisms. Ion channel myopathies such as paramyotonia congenita, hyper- and hypokalaemic periodic paralysis, myotonia congenita, episodic ataxia and malignant hyperthermia were established as linked to mutations in genes encoding the sodium channel, dihydropyridine receptor, chloride channel, potassium channel and the ryanodine receptor calcium release channel, respectively. Metabolic disorders affecting skeletal muscle were found to be due to deficiencies in a variety of enzymes. Identification of defects in components belonging to the gigantic dystrophin-glycoprotein complex led to the discovery of the molecular pathogenesis of Duchenne muscular dystrophy and related disorders. Based on these molecular findings, it is now feasible to design and evaluate new techniques such as gene and myoblast transfer therapy in order to replace defective components in diseased muscle fibres.
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PMID:[Molecular pathogenesis of muscular diseases]. 903 37

Some of the most common diseases in humans occur intermittently in people who are otherwise healthy and active. Such disorders include migraine headache, epilepsy, and cardiac arrhythmias. Because electrical signals are critical to the function of neurons, muscle cells, and heart cells, proteins that regulate electrical signaling in these cells are logical sites where abnormalities might lead to disease. All of these diseases have prominent genetic components. Difficulty in understanding these diseases arises from the complexity of the clinical phenotypes as well as from the genetic heterogeneity that is almost certain to exist. Therefore, early work in may laboratory was aimed at understanding the pathogenesis of rare disorders that are similar in their episodic nature. These disorders of muscle (the periodic paralyses), lead to attacks of weakness that occur intermittently in otherwise normal people. We, and others, have shown that hyperkalemic periodic paralysis (hyperKPP) and paramyotonia congenita (PC) result from mutations in a gene encoding a skeletal muscle sodium channel. We have also shown that hypokalemic periodic paralysis (hypoKPP) is caused by mutations in a gene encoding a voltage-gated calcium channel. The characterization of these diseases as channelopathies has served as a paradigm for other episodic disorders. One example is periodic ataxia, which results from mutations in voltage-gated potassium calcium channels. Long QT syndrome, an episodic cardiac dysrhythmia syndrome, is known to result from mutations in either voltage-gated sodium or potassium channels. We have recently mapped genes that cause a familial paroxysmal dyskinesia (non-kinesiogenic paroxysmal dystonia/choreoathetosis) in humans and a reflex epilepsy in mice. The similarities among all these disorders, including their episodic nature, precipitating factors, and therapeutic responses, are striking. Understanding gained from work in these rare monogenic episodic disorders is not only allowing characterization of the molecular and physiologic basis of these diseases, but may ultimately shed light on our understanding of the pathophysiology of more common and genetically complex disorders of the central nervous system.
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PMID:Channelopathies: ion channel disorders of muscle as a paradigm for paroxysmal disorders of the nervous system. 919 7

Since 1990, many mutations, in genes encoding ion channels have been discovered to cause disorders characterized by hyper- or hypoexcitability of skeletal muscle or the central nervous system (CNS): i) mutations in the muscle chloride channel gene lead to a loss or change of function of the channels and cause an abnormally low total chloride conductance resulting in hyperexcitability of the muscle fiber membrane in the dominant and recessive form of myotonia congenita; ii) numerous dominant point mutations in the gene encoding the muscle sodium channel alpha-subunit cause incomplete sodium channel inactivation. Dependent on the inactivation parameter altered and the degree of the gain of function induced by a given mutation, the muscle episodically becomes hyper- or hypoexcitable (i.e. stiff or weak), particularly in response to elevated serum potassium (potassium-aggravated myotonia, hyperkalemic periodic paralysis) or cold environment (paramyotonia congenita); iii) dominant point mutations in the gene coding for the muscle L-type calcium channel alpha(1)-subunit can cause episodes of muscle inexcitability (i.e. weakness), particularly in response to lowered serum potassium (hypokalemic periodic paralysis); despite the recently discovered etiology of the disease, the pathogenesis of the weakness is still unknown; iv) dominant mutations in a voltage-gated potassium channel expressed in the CNS cause episodic ataxia type 1 presumably by antagonizing repolarization of the cell membrane; v) dominant mutations in a neuronal calcium channel alpha-subunit may cause either episodic ataxia type II or familial hemiplegic migraine by a so far unknown pathomechanism; vi) the first mutation in an ion channel associated with an inherited form of epilepsy, nocturnal frontal lobe epilepsy, was found in the alpha(4)-subunit of a neuronal nicotinic acetylcholine receptor.
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PMID:[Ion channel diseases in neurology]. 948 Feb 90

Analysis of the molecular defects in mouse mutants can identify candidate genes for human neurological disorders. During the past 2 years, mutations in sodium channels, calcium channels and potassium channels have been identified by positional cloning of the spontaneous mouse mutants motor endplate disease, tottering, lethargic and weaver. The phenotypes of four allelic mutations identified in the sodium channel gene Scn8a range from ataxia and muscle weakness through severe dystonia and progressive paralysis, indicating that human mutations in this gene could be associated with a variety of clinical syndromes. Mutations of the calcium channel subunits beta 4 in the lethargic mouse and alpha 1A in the tottering mouse have specific effects on cerebellar function. Targeted mutation of ligand-gated ion channels has also been used to generate new models of neurological disease. We will review these recent achievements and their implications for human neurological disease. The mouse studies indicate that mutations in ion channel genes are likely to be responsible for a broad spectrum of clinical phenotypes in human neurological disorders.
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PMID:Ion channel mutations in mouse models of inherited neurological disease. 956 26

The mouse Scn8a sodium channel and its ortholog Na6 in the rat are abundantly expressed in the CNS. Mutations in mouse Scn8a result in neurological disorders, including paralysis, ataxia, and dystonia. In addition, Scn8a has been observed to mediate unique persistent and resurgent currents in cerebellar Purkinje cells (Raman et al., 1997). To examine the functional characteristics of this channel, we constructed a full-length cDNA clone encoding the mouse Scn8a sodium channel and expressed it in Xenopus oocytes. The electrophysiological properties of the Scn8a channels were compared with those of the Rat1 and Rat2 sodium channels. Scn8a channels were sensitive to tetrodotoxin at a level comparable to that of Rat1 or Rat2. Scn8a channels inactivated more rapidly and showed differences in their voltage-dependent properties compared with Rat1 and Rat2 when only the alpha subunits were expressed. Coexpression of the beta1 and beta2 subunits modulated the properties of Scn8a channels, but to a lesser extent than for the Rat1 or Rat2 channels. Therefore, all three channels showed similar voltage dependence and inactivation kinetics in the presence of the beta subunits. Scn8a channels coexpressed with the beta subunits exhibited a persistent current that became larger with increasing depolarization, which was not observed for either Rat1 or Rat2 channels. The unique persistent current observed for Scn8a channels is consistent with the hypothesis that this channel is responsible for distinct sodium conductances underlying repetitive firing of action potentials in Purkinje neurons.
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PMID:Functional analysis of the mouse Scn8a sodium channel. 969 4

The voltage-gated sodium channel SCN8A is associated with inherited neurological disorders in the mouse that include ataxia, dystonia, severe muscle weakness, and paralysis. We report the complete coding sequence and exon organization of the human SCN8A gene. The predicted 1980 amino acid residues are distributed among 28 exons, including two pairs of alternatively spliced exons. The SCN8A protein is evolutionarily conserved, with 98.5% amino acid sequence identity between human and mouse. Consensus sites for phosphorylation of serine/threonine and tyrosine residues are present in cyoplasmic loop domains. The polymorphic (CA)n microsatellite marker D12S2211, with PIC = 0.68, was isolated from intron 10C of SCN8A. Single nucleotide polymorphisms in intron 19 and exon 22 were also identified. We localized SCN8A to chromosome band 12q13.1 by physical mapping on a YAC contig. The cDNA clone CSC-1 was reported by others to be a cardiac-specific sodium channel, but sequence comparison demonstrates that it is derived from exon 24 of human SCN8A. The genetic information described here will be useful in evaluating SCN8A as a candidate gene for human neurological disease.
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PMID:Exon organization, coding sequence, physical mapping, and polymorphic intragenic markers for the human neuronal sodium channel gene SCN8A. 982 31

Voltage-gated sodium channels (NaCh) are colocalized with isoforms of the membrane-skeletal protein ankyrinG at axon initial segments, nodes of Ranvier, and postsynaptic folds of the mammalian neuromuscular junction. The role of ankyrinG in directing NaCh localization to axon initial segments was evaluated by region-specific knockout of ankyrinG in the mouse cerebellum. Mutant mice exhibited a progressive ataxia beginning around postnatal day P16 and subsequent loss of Purkinje neurons. In mutant mouse cerebella, NaCh were absent from axon initial segments of granule cell neurons, and Purkinje cells showed deficiencies in their ability to initiate action potentials and support rapid, repetitive firing. Neurofascin, a member of the L1CAM family of ankyrin-binding cell adhesion molecules, also exhibited impaired localization to initial segments of Purkinje cell neurons. These results demonstrate that ankyrinG is essential for clustering NaCh and neurofascin at axon initial segments and is required for physiological levels of sodium channel activity.
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PMID:AnkyrinG is required for clustering of voltage-gated Na channels at axon initial segments and for normal action potential firing. 983 57


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