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S H Subramony

Publications and source records attributed to S H Subramony.

At least 55 records · Page 3Linked to original sources
PubMed1995

Gametic and somatic tissue-specific heterogeneity of the expanded SCA1 CAG repeat in spinocerebellar ataxia type 1.

Spinocerebellar ataxia type 1 is associated with expansion of an unstable CAG repeat within the SCA1 gene. Male gametic heterogeneity of the expanded repeat is demonstrated using single sperm and low-copy genome analysis. Low-copy genome analysis of peripheral blood also reveals somatic heterogeneity of the expanded SCA1 allele, thus establishing mitotic instability at this locus. Comparative analysis of a large normal allele and a small affected allele suggests a role of midstream CAT interspersions in stabilizing long (CAG)n stretches. Within the brain, tissue-specific mosaicism of the expanded allele is also observed. The differences in SCA1 allele heterogeneity between sperm and blood and within the brain parallels the findings in Huntington disease, suggesting that both disorders share a common mechanism for tissue-specific instability.

Alleles↗
PubMed1995

Clinical aspects of hereditary ataxias.

The hereditary ataxias are a group of complex genetic disorders the understanding of which is undergoing a revolution because of advances in molecular genetics. Within the last few years, at least seven different gene loci have been found to be responsible for these syndromes, and the search is on for additional loci that undoubtedly exist. This review summarizes the clinical features of the various hereditary ataxias with known gene loci, as well as others that are now defined on a clinical basis. It also deals with some of the imaging and neuropharmacologic advances that have been made in this group of disorders.

Adult↗
PubMed1995

Daunomycin inhibits insulin-like growth factor I-dependent protein tyrosine phosphorylation.

The effect of the antitumor antibiotic daunomycin (DN) was studied on insulin-like growth factor I (IGF-I)-dependent protein tyrosine phosphorylation. DN was found to inhibit IGF-I-dependent phosphorylation of the artificial substrate poly(Glu:Tyr)4:1 by intrinsic IGF-I receptor kinase either from mouse cerebellum or from rat spinal cord. IGF-I-dependent autophosphorylation of the IGF-I receptor was also inhibited as a function of DN concentration (10-100 microM). However, DN at 200 microM concentration had minimal effect on protein kinase C dependent phosphorylation. The IGF-I-dependent protein tyrosine phosphorylation of endogenous proteins of the rat spinal cord was also inhibited by 50 microM DN. The altered IGF-I-dependent protein tyrosine phosphorylation by DN may partially explain its mechanism of action as an antitumor agent. These observations may also explain the neurotoxic effects of DN.

Animals↗
PubMed1995

Developmental changes in cerebellar endothelin-1 receptors in the neurologic mouse lurcher mutant.

In order to elucidate the role of neuromodulator endothelin-1 (ET-1) in cerebellar degeneration we determined ET-1 receptor binding in the control and lurcher mice cerebella at different postnatal (P) ages. The lurcher mutant is a suggested animal model for human cerebellar ataxias. The cerebellar membranes were prepared from 5 to 20 day old lurcher mice and littermate controls. ET-1 receptor binding was determined using radioligand assay and affinity cross-linking. There was a significant decrease in [125I]ET-1 receptor binding with increasing postnatal age in the control and lurcher mice cerebella. Lurcher mice showed a significant increase in [125I]ET-1 receptor binding at P 9 to P 20 as compared with the controls. Whereas, at P5 to P7 no significant change was observed. By autoradiography, ET-1 receptors were localized in tile granule cell layer of 15 day old control and lurcher mice cerebella. Whereas, the lUrcher mice showed an increase in [125I]ET-1 binding in the cerebellum as compared with the littermate controls. The results of the present study suggest that the increase in ET-1 receptor binding as early as P9 (when neuronal loss is minimal) in the lurcher mutant may reflect upregulation of ET-1 receptors in the degenerating neurons. At P 15 to P 20, when about 50% to 75% neurons are lost respectively, these changes may also reflect astrogliosis.

Age Factors↗
PubMed1994

Decreased insulin-like growth factor I-mediated protein tyrosine phosphorylation in human olivopontocerebellar atrophy and lurcher mutant mouse.

We examined insulin-like growth factor I (IGF-I)-dependent phosphorylation and protein tyrosine kinase (PTK) activity in cerebellar cortex of normal humans, patients with olivopontocerebellar atrophy (OPCA) ("C" kindred) and in lurcher mutant mouse, a suggested animal model for OPCA. PTK activity and IGF-I-dependent protein tyrosine phosphorylation was significantly reduced in cerebellar cortex of human OPCA patients as compared to the normal controls. Immunoblot analysis also demonstrated a decrease in cerebellar 80 kDa phosphotyrosine protein in these patients. By autoradiography, IGF-I receptors were localized in the molecular layer of 30-day-old control and lurcher mutant mice cerebella. However, the lurcher mutant mice showed a decrease in [125I]-IGF-I binding in the molecular layer as compared to the littermate controls. The IGF-I receptor autophosphorylation was also markedly reduced in 15-day- and 22-day-old lurcher cerebella. These results suggest that the process of cerebellar degeneration in human OPCA and lurcher mutant mouse may be associated with altered IGF-I receptor binding and protein tyrosine phosphorylation.

Amino Acid Sequence↗
PubMed1994

Degenerative ataxias.

This review summarizes recent advances that have taken place in the field of inherited ataxias. There is increasing understanding of these disorders, primarily because of advances in the field of molecular genetics. Although the Friedreich's ataxia gene has not been cloned yet, there is increasing information about the precise location of this mutation. The chromosomal location for a distinct type of recessive ataxia associated with vitamin E deficiency was discovered. An adult- onset Friedreich's phenotype may result from a gene abnormality of the same locus as classic Friedreich's ataxia. Two distinct types of dominantly inherited ataxic syndromes are due to different trinucleotide repeat mutations, one on chromosome 6 (spinocerebellar ataxia type 1) and another on chromosome 12 (dentatorubropallidoluysian atrophy). The genes for Machado-Joseph disease as well as for a distinct type of dominantly inherited ataxia originally described from Cuba were mapped to chromosome 14 and chromosome 12, respectively. Advances were made in defining the imaging abnormalities seen in different types of ataxias.

Adolescent↗
PubMed1994

Molecular and clinical correlations in spinocerebellar ataxia type I: evidence for familial effects on the age at onset.

The spinocerebellar ataxias are a group of debilitating neurodegenerative diseases for which a clinical classification system has proved unreliable. We have recently isolated the gene for spinocerebellar ataxia type 1 (SCA1) and have shown that the disease is caused by an expanded, unstable, CAG trinucleotide repeat within an expressed gene. Normal alleles have a size range of 19-36 repeats, while SCA1 alleles have 42-81 repeats. In this study, we examined the frequency and variability of the SCA1 repeat expansion in 87 kindreds with diverse ethnic backgrounds and dominantly inherited ataxia. All nine families for which linkage to the SCA1 region of 6p had previously been established showed repeat expansion, while 3 of the remaining 78 showed a similar abnormality. For 113 patients from the families with repeat expansion, inverse correlations between CAG repeat size and both age at onset and disease duration were observed. Repeat size accounted for 66% of the variation in age at onset in these patients. After correction for repeat size, interfamilial differences in age at onset remained significant, suggesting that additional genetic factors affect the expression of the SCA1 gene product.

Adolescent↗
PubMed1992

Inositol 1,4,5-trisphosphate metabolism in the cerebella of Lurcher mutant mice and patients with olivopontocerebellar atrophy.

We have investigated inositol 1,4,5-trisphosphate (InsP3) metabolism in cerebellar membranes of normal humans and patients with dominant ataxia ('C' kindred), and also in cerebellar microsomes of Lurcher mutant mouse (a suggested model for cerebellar ataxia). Various [3H]InsP3 metabolites formed were separated by HPLC using 3 successive convex gradients of 1.7 M ammonium formate, pH 3.7. [3H]InsP3 metabolism was rapid and in 15- and 45-day-old control mice cerebella about 50% of [3H]InsP3 was metabolized within 20 s. In 15-day-old Lurcher mice the rate of [3H]InsP3 metabolism was significantly low (40% of normal). [3H]InsP3 metabolism was almost absent in 45-day-old Lurcher mice cerebellar microsomes. The decreased [3H]InsP3 metabolism was consistent with decreased recovery of the various inositol polyphosphates formed. Similarly, in cerebellar membranes of human patients with olivopontocerebellar atrophy (OPCA) a significant decrease in [3H]InsP3 metabolism was observed when compared with normal controls. These data suggest that altered phosphoinositide turnover may be associated with the onset of neuronal degeneration in human OPCA.

Animals↗
PubMed1992

Case report: autonomic postganglionic denervation--sural nerve and saphenous vein biopsy.

The authors describe a 31-year-old woman of British Isle ancestry who developed a syndrome resembling familial dysautonomia in her early teenage years. Predominant manifestations included achalasia, severe orthostatic hypotension, and abnormal sweating. The study included resting and stimulated fractional catecholamines, which were almost nonexistent in both situations, and urinary catecholamines, demonstrating an increase in dopamine degradation products. Immunohistochemistry of saphenous vein was negative for dopamine beta-hydroxylase (DBH), serotonin (5-HT) and several vasoactive neuropeptides. The only neuropeptide detected at levels thought to be physiologically relevant was calcitonin gene-related peptide (CGRP), a vasodilator. This was in contrast to control veins, all of which had DBH and neuropeptide Y immunoreactive fibers but few CGRP fibers. Also in contrast to controls, electron microscopy of the saphenous vein indicated a close to total absence of terminals with norepinephrine containing vesicles. Sural nerve biopsy showed, on electron microscopy, a considerable reduction in the number of myelinated fibers, while unmyelinated fibers appeared to be in the normal range. The authors suggest, from the above findings, that the autonomic fibers were undergoing some form of distal axonal degeneration. Their findings differ from most biopsies performed in dysautonomic children, and they believe their patient has a different neurologic entity.

Adult↗
PubMed1992

Stiff-man syndrome.

Stiff-man syndrome (SMS) is a rare disorder of the central nervous system characterized by painful involuntary stiffening of axial muscles accompanied by spasms. These are often precipitated by tactile or emotional stimuli, volitional movement, and startling noises. Until recently, little has been known about the pathogenesis of SMS. There is evidence now to support the hypothesis that SMS may be an autoimmune disease. This is leading to changes in the way this disease is diagnosed and treated. We describe two patients with SMS and review the pathogenesis, diagnosis, and treatment.

Adult↗
PubMed1991

Inositol 1,4,5-trisphosphate receptors and protein kinase C in olivopontocerebellar atrophy.

We examined protein kinase C (PKC) activity and inositol 1,4,5-trisphosphate (InsP3) binding in frontal cortex (FC) and cerebellar cortex (CC) of normal humans, patients with dominant ataxia ("C" kindred) and in Lurcher mutant mouse brain (LMB), a suggested animal model for olivopontocerebellar atrophy (OPCA). PKC activity and [3H]InsP3 binding were decreased in CC of human OPCA by 70% and 90% respectively. The decreases were specific to CC as there were no changes in FC. PKC activity and [3H]InsP3 binding in cerebellum (CB) of LMB were similarly decreased as compared to normal littermate controls. The LMB decrease of PKC and [3H]InsP3 binding was evident on the 15th day of age, the day of onset of ataxia. InsP3-mediated calcium release was also decreased significantly in the cerebellar microsomes of 25-day-old LMB and human OPCA when compared with their respective controls. These data indicate that the decrease of second messenger linked PKC activity and InsP3 receptor binding in CB may be a biochemical marker that reflects neuronal degeneration in dominant cerebellar ataxia.

Animals↗
PubMed1988

AAEE case report #14: neuralgic amyotrophy (acute brachial neuropathy).

Neuralgic amyotrophy is characterized by acute onset of arm pain, followed after a variable interval by flaccid paralysis in the distribution of the brachial plexus on one or sometimes both sides. Electromyography reveals findings suggestive of an axonal degeneration process affecting various portions of the brachial plexus or individual nerves emanating from it, sometimes difficult to localize to discrete cords, trunks, or nerves. Diagnosis is established by excluding other causes, including compression and vasculitides. Prognosis for recovery is excellent.

Acute Disease↗
PubMed1986

Motor neuropathy associated with a facilitating myasthenic syndrome.

We report a patient with progressive muscle weakness, areflexia, and no sensory loss. Electromyography revealed normal sensory nerve conductions, mild slowing of motor nerve conduction velocities, low amplitude compound muscle action potentials, a neuromuscular transmission defect characterized by prominent facilitation, and diffuse fibrillation potentials. Muscle biopsies showed acute denervation atrophy, and at autopsy, there was anterior horn cell loss and gliosis in the spinal cord. The findings suggest the coexistence of a motor neuropathy and a facilitating myasthenic syndrome.

Action Potentials↗
PubMed1986

Lack of cold sensitivity in hyperkalemic periodic paralysis.

The nosologic distinction between paramyotonia congenita and hyperkalemic periodic paralysis is somewhat blurred. Muscle membrane inexcitability induced by cooling seems to be characteristic of paramyotonia congenita. The effect of cooling on the maximal compound muscle action potential (CMAP) in patients with paramyotonia congenita was compared to that in patients with hyperkalemic periodic paralysis. Diminution in CMAP amplitude and area, which was observed in paramyotonia congenita, did not occur in hyperkalemic periodic paralysis. We suggest that this effect of cooling on the CMAP can be utilized in the differentiation of these two syndromes.

Action Potentials↗
PubMed1986

Systemic lupus erythematosus presenting with recurrent acute demyelinating polyneuropathy.

We report a patient who in the course of 3 years developed 3 distinct episodes of an acute demyelinating neuropathy, each fulfilling the criteria set up by an ad hoc committee of the National Institute of Neurological and Communicative Disorders and Stroke for acute Guillain-Barré syndrome. Each episode was associated with strong serological evidence for lupus erythematosus. The episodes were separated by 1-2 years and each was followed by near complete clinical recovery. The only systemic feature was a pleural effusion during the last 2 episodes.

Acute Disease↗