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)

Downbeat nystagmus (DBN) is the most frequent form of acquired persisting fixation nystagmus. It is hypothesized to occur when physiological inhibitory cerebellar input, namely of the flocculus, to the vestibular nuclei is inhibited. The second most frequent form of acquired nystagmus is upbeat nystagmus (UBN). UBN is probably caused by an imbalance of vertical vestibulo-ocular reflex tone. GABA-ergic substances like baclofen have been used to treat DBN and UBN, but they have had only moderate success. Animal experiments have shown that aminopyridines [3,4-diaminopyridine (3,4-DAP) and 4-aminopyridine (4-AP)], nonselective blockers of the Kv family of voltage-gated potassium channels, increase Purkinje-cell (PC) excitability. It was assumed that such enhancement of PC activity could restore to normal levels the inhibitory influence of the cerebellar cortex on vertical eye movements. On the basis of these assumptions, we evaluated the efficacy and underlying mechanisms of aminopyridines in DBN and UBN as well as in another cerebellar disorder with an impaired PC function: episodic ataxia type 2 (EA2), which is caused by mutations of the PQ-calcium channel. In a placebo-controlled trial on 17 patients we demonstrated that 3,4-DAP significantly reduces the intensity of DBN. This was confirmed in a recent study with 4-AP, which also showed that 4-AP restores gaze-holding ability independently of fixation in DBN. The efficacy of 4-AP in UBN was demonstrated in single patients. Finally, in an open trial on three patients with EA2 we showed that 4-AP prevents attacks of ataxia. This was also found in an animal model (the tottering mouse) of EA2. The clinical efficacy of 4-AP in EA2 is being further evaluated in an ongoing randomized controlled crossover trial. In conclusion, the use of aminopyridines in DBN, UBN, and EA2 is a new treatment principle for vestibular, cerebellar, and ocular motor disorders.
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PMID:Aminopyridines for the treatment of cerebellar and ocular motor disorders. 1871 50

"Ryegrass staggers" is a neurological condition of unknown mechanism that impairs motor function in livestock. It is caused by infection of perennial ryegrass pastures by an endophytic fungus that produces neurotoxins, predominantly the indole-diterpenoid compound lolitrem B. Animals grazing on such pastures develop uncontrollable tremors and become uncoordinated in their movement. Lolitrem B and the structurally related tremor inducer paxilline both act as potent large conductance calcium-activated potassium (BK) channel inhibitors. Using patch clamping, we show that their different apparent affinities correlate with their toxicity in vivo. To investigate whether the motor function deficits produced by lolitrem B and paxilline are due to inhibition of BK ion channels, their ability to induce tremor and ataxia in mice deficient in this ion channel (Kcnma1(-/-)) was examined. Our results show that mice lacking Kcnma1 are unaffected by these neurotoxins. Furthermore, doses of these substances known to be lethal to wild-type mice had no effect on Kcnma1(-/-) mice. These studies reveal the BK channel as the molecular target for the major components of the motor impairments induced by ryegrass neurotoxins. Unexpectedly, when the response to lolitrem B was examined in mice lacking the beta4 BK channel accessory subunit (Kcnmb4(-/-)), only low-level ataxia was observed. Our study therefore reveals a new role for the accessory BK beta4 subunit in motor control. The beta4 subunit could be considered as a potential target for treatment of ataxic conditions in animals and in humans.
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PMID:The molecular mechanism of "ryegrass staggers," a neurological disorder of K+ channels. 1880 45

The Shaker family voltage-dependent potassium channels (Kv1) are expressed in a wide variety of cells and are essential for cellular excitability. In humans, loss-of-function mutations of Kv1 channels lead to hyperexcitability and are directly linked to episodic ataxia and atrial fibrillation. All Kv1 channels assemble with beta subunits (Kv betas), and certain Kv betas, for example Kv beta 1, have an N-terminal segment that closes the channel by the N-type inactivation mechanism. In principle, dissociation of Kv beta 1, although never reported, should eliminate inactivation and thus potentiate Kv1 current. We found that cortisone increases rat Kv1 channel activity by binding to Kv beta 1. A crystal structure of the Kv beta-cortisone complex was solved to 1.82-A resolution and revealed novel cortisone binding sites. Further studies demonstrated that cortisone promotes dissociation of Kv beta. The new mode of channel modulation may be explored by native or synthetic ligands to fine-tune cellular excitability.
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PMID:Cortisone dissociates the Shaker family K+ channels from their beta subunits. 1893 45

A 13-mo-old intact male African lion (Panthera leo) presented with a 3-mo history of lethargy, ventral flexion of the neck, abnormal vocalization, and ataxia. Hemogram and serum biochemistries were within normal limits except for the presence of hypokalemia (2.7 mEq/L) and hypochloridemia (108 mEq/L). When no improvement was noted with oral potassium gluconate supplementation, a computed tomography scan of the brain and skull was performed, and no abnormalities were noted. However, magnetic resonance imaging detected occipital bone thickening, crowding of the caudal cranial fossa with cerebellar compression and herniation, and cervical syringohydromyelia, which was consistent with a Chiari I-like malformation. Foramen magnum decompression was performed to relieve the compression of the cerebellum. The animal recovered well with subsequent resolution of clinical signs. Hypovitaminosis A has been proposed previously as the underlying etiology for this malformation in lions with similar clinical presentations. This lion's serum and liver vitamin A concentrations were low (100 ng/ml and 25.31 microg/g, respectively) compared to concentrations reported for domestic carnivores and support hypovitaminosis A as the underlying cause of this animal's Chiari I-like malformation.
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PMID:Diagnosis and surgical treatment of a Chiari I-like malformation in an African lion (Panthera leo). 1881 6

Potassium ion channels play critical roles in cell function, providing the maintenance of the membrane, repolarization of action potentials, and the regulation of firing frequency. Mutations in genes that interfere with K(v) ion channel function cause severe inherited diseases, such as episodic ataxia type 1, deafness, epilepsy, or cardiac arrhythmia. Because of their critical role in the central nervous system, all ion channels are targets for multiple pharmacologically active compounds. Better understanding of the structure and function of K(v) channels may eventually contribute to a more effective design of drugs. In this review, we show the recent data about domain organization of eukaryotic potassium voltage-gated ion channels. We are giving special attention to the interaction between the domains and the corresponding conformational changes upon activation of the channel.
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PMID:The domain and conformational organization in potassium voltage-gated ion channels. 1883 41

Watery diarrhoea, hypokalaemia and achlorhydria (WDHA) syndrome was caused by vasoactive intestinal polypeptide (VIP)-producing tumour. A 3-year-old Chinese girl with watery diarrhoea, abdominal distension and hypokalaemia due to a thoracic paraspinal VIP-secreting ganglioneuroma is reported. The girl coughed, fevering up to 39 degrees C after a flu-like episode. She had eight to ten abundant stools daily which is not improved by dietary treatment, resulting in an important weight loss. She weighed 6.8 kg (nl P50 at 6 months of age) and is 76 cm (nl P50 at 9 months of age) in height. Blood electrolytes showed 129 mmol/L sodium, 2.42 mmol/L potassium, 94 mmol/L chloride and 18.6 mmol/L bicarbonate; urinary catecholamines were normal. Computed tomography scan evidenced a left side paravertebral mass of 4 x 6 cm in the lower thoracic region leading to the blood determination of vasoactive intestinal polypeptide which amounted 830 pmol/L(normal < 25 pmol/L). Surgical removal showed a ganglioneuroma of 160 g and was associated with disappearance of the diarrhoea and normalization of VIP level below 20 pmol/L. Review of the 63 reported cases in children with WDHA showed that many of the cases presented with non-treatable watery diarrhoea, hypokalaemia. Achlorhydria is not necessarily part of the WDHA syndrome. The male to female ratio is 1:1.5. Ganglioneuroblastoma and ganglioneuroma are the commonest tumours. Location of the tumour is variable: abdomen, chest or neck. Abdominal distension, flushing, episodic hypertension and colonic dilatation, constipation and ataxia were the other associated features. Surgical resection is the treatment of choice of VIP-producing tumours.
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PMID:Tumor with watery diarrhoea, hypokalaemia in a 3-year-old girl. 1910 28

Different subunits of the Kv3 subfamily of voltage-gated potassium (Kv) channels (Kv3.1-Kv3.4) are expressed in distinct neuronal subpopulations in the cerebellum. Behavioral phenotypes in Kv3-null mutant mice such as ataxia with prominent hypermetria and heightened alcohol sensitivity are characteristic of cerebellar dysfunction. Here, we review how the unique biophysical properties of Kv3-type potassium channels, fast activation and fast deactivation that enable cerebellar neurons to generate brief action potentials at high frequencies, affect firing patterns and influence cerebellum-mediated behavior.
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PMID:The role of Kv3-type potassium channels in cerebellar physiology and behavior. 1924 32

Limbic encephalitis is an inflammatory disease localized to the "grand lobe limbique" defined by Broca in 1878, sometimes restricted to the hippocampus, but sometimes including extralimbic abnormalities. The main features are subacute onset, short-term memory disorders and cognitive impairment, temporal seizures, and hippocampic changes on MRI. A list of underlying causes has recently been published Infectious causes used to be frequent (mainly herpes simplex virus). Paraneoplastic limbic encephalitis is characterized by the presence of various onconeural antibodies, such as AntiHu and ANNA3 (bronchial small cell carcinoma), AntiMa2 (testicular tumor), AntiCV2 (lymphoma, thymoma,...). No such antibodies are detected in 40% of patients. The prognosis of these forms is poor. Voltage-gated potassium channel-associated limbic encephalopathies are due to antibodies targeting potassium channels. Mutations of the genes encoding the Kv11 and Kv12 subunits are responsible for several Shaker syndromes, including neuromyotonia, Morvan's disease, type I episodic ataxia, and limbic encephalitis with hyponatremia. Plasma exchanges and immunotherapy are effective. In patients without detectable antibodies, hippocampic anti-neuropil antibodies should be sought, particularly those targeting N-methyl-D-aspartate receptors. Ovarian teratoma is the usual cause of this type of encephalitis. Surgery and immunotherapy are effective. These disorders have been categorized into those associated with antibodies targeting intracellular antigens (poor-prognosis paraneoplastic encephalitis) and those associated with antibodies targeting antigens reacting with cellular membranes (potassium channelopathies and antineuropil antibodies), which respond to immunotherapy and carry a better prognosis. Limbic encephalitis can also reveal Hodgkin's disease, as in a case observed by the authors.
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PMID:[Limbic encephalitis--evolving concepts]. 1944 70

Gabapentin (GBP) is a drug which is frequently used in diabetic neuropathy. Common adverse effects of GBP include drowsiness, dizziness, ataxia, somnolence, and fatigue. Rhabdomyolysis is an extremely rare side effect of GBP. In this report we describe a case of GBP-induced rhabdomyolysis in a 63-year-old diabetic woman. She presented with severe muscle pain in her extremities, fatigue, decreased urine output and urine discoloration within 3 weeks after starting treatment with GBP (900 mg/day) for diabetic neuropathy. Laboratory tests revealed extreme elevations of muscle enzymes, increased creatinine and potassium levels. She required hemodialysis as a result of anuria. Investigation confirmed the diagnosis of rhabdomyolysis, and discontinuation of GBP resulted in resolution of clinical and biochemical features of rhabdomyolysis.
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PMID:Gabapentin-induced rhabdomyolysis in a patient with diabetic neuropathy. 1952 4

Clinical neurophysiology has become an invaluable tool in the diagnosis of muscle channelopathies, but the situation is less clear cut with neuronal channelopathies. The genetic episodic ataxias are a group of disorders with heterogeneous phenotype and genotype, but share in common the feature of intermittent cerebellar dysfunction. Episodic ataxia (EA) types 1 and 2 are the most widely recognised of the autosomal dominant episodic ataxias and are caused by dysfunction of neuronal voltage-gated ion channels. There are central and peripheral nervous system manifestations in both conditions, and they are therefore good models of neuronal channelopathies to study neurophysiologically. To date most work has focussed upon characterising the electrophysiological properties of mutant channels in vitro. This review summarises the role of voltage-gated potassium and calcium channels, mutations of which underlie the main types of episodic ataxia types 1 and 2. The clinical, genetic and electrophysiological features of EA1 and EA2 are outlined, and a protocol for the assessment of these patients is proposed.
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PMID:Clinical neurophysiology of the episodic ataxias: insights into ion channel dysfunction in vivo. 1973 86


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