Biomedical subjects

M G Sweeney

Publications and source records attributed to M G Sweeney.

39 records · Page 3Linked to original sources

PubMed1992

Evidence against an X-linked locus close to DXS7 determining visual loss susceptibility in British and Italian families with Leber hereditary optic neuropathy.

Leber hereditary optic neuropathy (LHON) is associated with mutations of mtDNA, but two features of LHON pedigrees are not explicable solely on the basis of mitochondrial inheritance. There is a large excess of affected males, and not all males at risk develop the disease. These observations could be explained by the existence of an X-linked visual loss susceptibility gene. This hypothesis was supported by linkage studies in Finland, placing the susceptibility locus at DXS7, with a maximum lod score of 2.48 at a recombination fraction of 0. Linkage studies in 1 Italian and 12 British families with LHON, analyzed either together or separately depending on the associated mtDNA mutation, have excluded the presence of such a locus from an interval of about 30 cM around DXS7 in these kindreds, with a total lod score of -26.51 at a recombination fraction of 0.

Base Sequence↗

PubMed1992

Prenatal diagnosis of mitochondrial DNA8993 T----G disease.

We have previously described a family with a neurological syndrome comprising neurogenic muscle weakness, ataxia, retinitis pigmentosa, and variable sensory neuropathy, seizures, and mental retardation or dementia. This is associated with a heteroplasmic point mutation of mtDNA at bp 8993. The mother of a severely affected child underwent prenatal diagnosis in two further pregnancies. Analysis of chorionic villus samples showed a higher proportion of mutant mtDNA on both occasions, and this was reflected in the majority of fetal tissues, including brain and muscle. Prenatal diagnosis is a rational approach to the prevention of severe diseases caused by point mutations of mtDNA but is currently hampered by incomplete knowledge concerning the proportion of mutant mtDNA: its relationship to disease severity, how it may change during fetal and postnatal development, and its tissue distribution.

Child, Preschool↗

PubMed1991

Mitochondrial encephalopathies: molecular genetic diagnosis from blood samples.

Point mutations of mitochondrial DNA have been described in the muscle of patients with syndromes of myoclonic epilepsy and ragged red fibres (MERRF) and of mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS). We have found the MERRF mutation in members of 6 British kindreds; 2 of these had unusual phenotypes but all index patients had myoclonus. The MELAS mutation was detected in 17 patients from 16 families, who had a wide range of clinical features that particularly affected the central nervous system; stroke-like episodes were observed in 10.3 patients with mitochondrial DNA mutations did not have ragged red fibres on muscle biopsy, generally considered to be the morphological hallmark of mitochondrial diseases. In all 6 patients with the MERRF mutation, and 10 of 11 with the MELAS mutation, the genetic defect was easily detected in blood cells as well as muscle (blood samples were not available in 6 patients with MELAS mutations in muscle). Molecular genetic analysis of blood samples represents an inexpensive and reliable screening test for mitochondrial encephalopathies, and use of such techniques could influence diagnosis and genetic counselling in patients with seizure disorders and young-onset stroke.

Acidosis, Lactic↗