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K Christodoulou

Publications and source records attributed to K Christodoulou.

At least 19 recordsLinked to original sources
PubMed2006

Phenotypic and cellular expression of two novel connexin32 mutations causing CMT1X.

OBJECTIVE: To determine the phenotypic and cellular expression of two novel connexin32 (Cx32) mutations causing X-linked Charcot-Marie-Tooth disease (CMT1X). METHODS: The authors evaluated several members of two families with CMT1X clinically, electrophysiologically, pathologically, and by genetic testing. The Cx32 mutations were expressed in vitro and studied by immunocytochemistry. RESULTS: In both families, men were more severely affected than women with onset in the second decade of life. In the first family, the phenotype was that of demyelinating polyneuropathy with variable involvement of peripheral nerves. There was clinical evidence of CNS involvement in at least three of the patients, with extensor plantar responses and brisk reflexes. In the second family, the affected man presented with symmetric polyneuropathy and intermediate slowing of conduction velocities, whereas affected women had prominent asymmetric atrophy of the leg muscles. The authors identified two novel missense mutations resulting in L143P amino acid substitution in the first family and in V140E substitution in the second family, both located in the third transmembrane domain of Cx32. Expression of these Cx32 mutations in communication-incompetent HeLa cells and immunocytochemical analysis revealed that both mutants were retained intracellularly and were localized in the Golgi apparatus. In contrast to wild-type protein, they did not form gap junctions. CONCLUSION: These novel connexin32 (Cx32) mutations cause a spectrum of clinical manifestations characteristic of Charcot-Marie-Tooth disease (CMT1X), including demyelinating or intermediate polyneuropathy, which is often asymmetric, and CNS involvement in one family. The position and cellular expression of Cx32 mutations alone cannot fully predict these phenotypic variations in CMT1X.

Aged↗
PubMed2002

Linkage of otosclerosis to a third locus (OTSC3) on human chromosome 6p21.3-22.3.

Clinical otosclerosis (OMIM 166800/605727) has a prevalence of 0.2-1% among white adults, making it the single most common cause of hearing impairment in this group. It is caused by abnormal bone homeostasis of the otic capsule with the consequent development of sclerotic foci that invade the stapedio-vestibular joint (oval window) interfering with free motion of the stapes. Impaired ossicular chain mobility results in a conductive hearing loss. We identified the first locus for otosclerosis (OTSC1) on chromosome 15 in 1998 and reported a second locus (OTSC2) on chromosome 7 last year. Here we present results of a genome wide linkage study on a large Cypriot family segregating otosclerosis. Results of this study exclude linkage to OTSC1 and OTSC2 and identify a third locus, OTSC3, on chromosome 6p. The defined OTSC3 interval covers the HLA region, consistent with reported associations between HLA-A/HLA-B antigens and otosclerosis.

Chromosome Mapping↗
PubMed2001

Mapping of the second Friedreich's ataxia (FRDA2) locus to chromosome 9p23-p11: evidence for further locus heterogeneity.

Friedreich's ataxia (FRDA), the most-common form of autosomal recessive ataxia, is inherited in most cases by a large expansion of a GAA triplet repeat in the first intron of the frataxin (X25) gene. Genetic heterogeneity in FRDA has been previously reported in typical FRDA families that do not link to the FRDA locus on chromosome 9q13. We report localization of a second FRDA locus (FRDA2) to chromosome 9p23-9p11, and we provide evidence for further genetic heterogeneity of the disease, in a family with the classic FRDA phenotype.

Adult↗
PubMed2001

Enzymatic treatment of sanitary landfill leachate.

The objective of this investigation was to study the effectiveness of applying enzymes (bioaugmentation) for enhancement of biological treatability of leachates generated in a typical municipal solid waste sanitary landfill. The basic purpose of enzyme use is to enforce the biodecomposition of organic constituents, as well as to reduce nitrogen content. A laboratory-scale sequencing batch (bio)reactor (SBR) was used for the examination of enzymatic application. The effect of different operation strategies on the efficiency of this biological treatment process was studied to optimize performance, especially for the removal of nitrogen compounds and of biodegradable organic matter. It was found that the enzymatic process was able to remove organic matter effectively (expressed as BOD5 and COD) and nitrogen content, color and turbidity.

Biodegradation, Environmental↗
PubMed2001

Treatment of proctalgia fugax with botulinum A toxin.

Two recent studies described a temporal association between a high-amplitude and high-frequency myoelectrical activity of the anal sphincter and the occurrence of proctalgia, which suggest that paroxysmal hyperkinesis of the anus may cause proctalgia fugax. We describe a single case of proctalgia fugax responding to anal sphincter injection of Clostridium botulinum type A toxin. The presumed aetiology of proctalgia fugax is discussed and the possible mechanism of action of botulinum toxin (BTX) in this condition is outlined. Botulinum A toxin seems to be a promising treatment for patients with proctalgia fugax, and further trials appear to be worthwhile for this condition, which has been described as incurable.

Botulinum Toxins, Type A↗
PubMed2000

An Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM) linked to chromosome 9p1.

We report an Italian family with autosomal recessive quadriceps-sparing inclusion-body myopathy (ARQS-IBM). The patients (two second cousins) developed a slowly progressive distal and proximal myopathy with complete sparing of the quadriceps. Muscle biopsy showed rimmed vacuoles in numerous muscle fibers, and electron microscopy documented accumulation of 15-21 nm filaments. DNA analysis established linkage to 9p1 and haplotype analysis revealed that the patients shared a recombined common haplotype. The gene locus of ARQS-IBM was initially mapped to chromosome 9p1-q1 in families of Iranian-Jewish origin and later confirmed in a few other ethnic groups. This is the first report of Italian patients with ARQS-IBM showing positive linkage to chromosome 9p1. Our data suggest that patients having distal and proximal myopathy with rimmed vacuoles and possible recessive inheritance, often classified as distal myopathies, should be thoroughly investigated according to the diagnostic criteria of h-IBM and, when positive, studied for linkage to chromosome 9p1.

Arm↗
PubMed2000

Charcot-Marie-Tooth type 4B is caused by mutations in the gene encoding myotubularin-related protein-2.

A gene mutated in Charcot-Marie-Tooth disease type 4B (CMT4B), an autosomal recessive demyelinating neuropathy with myelin outfoldings, has been mapped on chromosome 11q22. Using a positional-cloning strategy, we identified in unrelated CMT4B patients mutations occurring in the gene MTMR2, encoding myotubularin-related protein-2, a dual specificity phosphatase (DSP).

Alternative Splicing↗
PubMed2000

Fundamental gating mechanism of nicotinic receptor channel revealed by mutation causing a congenital myasthenic syndrome.

We describe the genetic and kinetic defects in a congenital myasthenic syndrome due to the mutation epsilonA411P in the amphipathic helix of the acetylcholine receptor (AChR) epsilon subunit. Myasthenic patients from three unrelated families are either homozygous for epsilonA411P or are heterozygous and harbor a null mutation in the second epsilon allele, indicating that epsilonA411P is recessive. We expressed human AChRs containing wild-type or A411P epsilon subunits in 293HEK cells, recorded single channel currents at high bandwidth, and determined microscopic rate constants for individual channels using hidden Markov modeling. For individual wild-type and mutant channels, each rate constant distributes as a Gaussian function, but the spread in the distributions for channel opening and closing rate constants is greatly expanded by epsilonA411P. Prolines engineered into positions flanking residue 411 of the epsilon subunit greatly increase the range of activation kinetics similar to epsilonA411P, whereas prolines engineered into positions equivalent to epsilonA411 in beta and delta subunits are without effect. Thus, the amphipathic helix of the epsilon subunit stabilizes the channel, minimizing the number and range of kinetic modes accessible to individual AChRs. The findings suggest that analogous stabilizing structures are present in other ion channels, and possibly allosteric proteins in general, and that they evolved to maintain uniformity of activation episodes. The findings further suggest that the fundamental gating mechanism of the AChR channel can be explained by a corrugated energy landscape superimposed on a steeply sloped energy well.

Cell Line↗
PubMed2000

Ursodeoxycholic acid (UDCA) for the treatment of amoxycillin-clavulanate potassium (Augmentin)-induced intra-hepatic cholestasis: report of two cases.

This report describes two patients who developed jaundice within two weeks of receiving an amoxycillin-clavulanate potassium combination. Causes of jaundice, other than drug administration, were excluded. The patients' jaundice and clinical symptoms did not respond to stopping the drug. Ursodeoxycholic acid (750 mg/day) led to a prompt and sustained improvement in their hyperbilirubinaemia and symptoms such as pruritus and fatigue. These cases suggest that ursodeoxycholic acid may be an effective treatment for drug-associated cholestasis.

Aged↗
PubMed2000

A novel form of distal hereditary motor neuronopathy maps to chromosome 9p21.1-p12.

Distal hereditary motor neuronopathies (dHMNs) form a heterogeneous group of rare disorders characterized by distal weakness and wasting in the limbs with no significant sensory involvement. Harding has classified dHMNs into seven categories based on clinical and genetic criteria. We report a novel form of autosomal recessive dHMN in 7 consanguineous families located in the Jerash region of Jordan. Onset of the disease is between 6 and 10 years of age and is characterized by weakness and atrophy of the lower limbs associated with pyramidal features. Within 2 years, symptoms progress to the upper limbs. Neurophysiological studies typically show normal conduction velocities, reduced compound motor action potential amplitudes, normal sensory nerve action potentials, and chronic neurogenic changes on needle electromyography. No significant abnormalities are seen on sural nerve biopsy. We call this novel form of dHMN Jerash hereditary motor neuronopathy. We studied the families at the molecular genetic level and mapped the Jerash hereditary motor neuronopathy gene to an approximately 0.54-cM region on chromosome 9p21.1-p12, flanked by microsatellite polymorphic marker loci D9S1845 and D9S1791. A maximum LOD score of 19.80 at theta = 0.001 was obtained between the disease and locus D9S1878.

Adolescent↗
PubMed1999

Chromosome 17p-linked myasthenias stem from defects in the acetylcholine receptor epsilon-subunit gene.

OBJECTIVE: To identify and to characterize functionally the mutational basis of congenital myasthenic syndromes (CMS) linked to chromosome 17p. BACKGROUND: A total of 37 patients belonging to 13 CMS families, 9 of them consanguineous, were investigated. All patients were linked previously to the telomeric region of chromosome 17p. Two candidate genes in this region encode synaptobrevin 2, a presynaptic protein, and the epsilon-subunit of the acetylcholine receptor (AChR). Direct sequencing of the synaptobrevin 2 gene revealed no mutations. The authors thus searched for mutations in the epsilon-subunit gene of AChR. METHODS: Direct sequencing of the AChR epsilon-subunit, restriction analysis, allele-specific PCR, and expression studies in human embryonic kidney cells were performed. RESULTS: The authors identified two previously characterized and five novel epsilon-subunit gene mutations, all homozygous, in the 13 kinships. Two of the novel mutations are truncating (epsilon723delC and epsilon760ins8), one is a missense mutation in the signal peptide region (epsilonV-13D), one is a missense mutation in the N-terminal extracellular domain (epsilonT51P), and one is a splice donor site mutation in intron 10 (epsilonIVS10+2T-->G). Unaffected family members have no mutations or are heterozygous. Expression studies indicate that the four novel mutations in the coding region of the gene and the most likely transcript of the splice-site mutation, which skips exon 10, are low-expressor or null mutations. CONCLUSIONS: Chromosome 17p-linked congenital myasthenic syndromes are caused by low-expressor/null mutations in the AChR epsilon-subunit gene. Mutations in this gene are a common cause of CMS in eastern Mediterranean countries.

Adolescent↗
PubMed1999

Distal hereditary motor neuronopathy of the Jerash type.

A novel form of autosomal recessive distal hereditary motor neuronopathy (distal HMN) is reported. The presence of pyramidal signs within the early stages of the disease with persistence of knee hyperreflexia form distinctive clinical features. We have mapped the HMN-J gene to chromosome 9p21.1-p12, within an estimated interval of 1.2-Mb.

Chromosome Mapping↗