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Biomedical subjects

E Byrne

Publications and source records attributed to E Byrne.

At least 127 records · Page 7Linked to original sources
PubMed1988

Protein synthesis in mitochondria isolated from human skeletal muscle. Detection of polymorphism in mitochondrial translation products.

The importance of the mitochondrial protein synthesizing system in the development of functional mitochondria, and thus presumably in the pathogenesis of mitochondrial cytopathies has become apparent in recent years. A procedure has been developed to allow the measurement of the protein synthetic activity in mitochondria isolated from human skeletal muscle biopsy materials. The examination of the mitochondrial protein synthesis products revealed two polymorphic variants with the electrophoretic mobilities in SDS-polyacrylamide gel of a 20/22 kDa and a 45/47 kDa protein. Since functional consideration suggests that these variants are most likely to be associated with conservative amino acid substitutions, the observation indicates that it might be possible to electrophoretically detect certain alterations in the mitochondrial translation products in mitochondrial cytopathies due to mutations in the mitochondrial genome.

Humans↗
PubMed1988

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS): adolescent onset with severe cerebral edema.

A 19-year-old woman with long-standing sensorineural deafness, bilateral cataracts and mild clumsiness, presented with acute focal edema in the left temperoparieto-occipital area which required surgical decompression as a life-saving measure. Investigation revealed a persistent lactic acidemia and evidence of many ragged red fibres in a skeletal muscle biopsy specimen, suggesting a diagnosis of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome. The patient developed two further stroke-like episodes over a short period. One sibling died at the age of 14 years with a progressive neurological illness characterised by seizures, bilateral optic atrophy, ataxia, myoclonus and progressive dementia. The diagnosis of MELAS syndrome should be considered in young people presenting with stroke-like episodes that fail to conform to a given vascular territory, particularly if they have long-standing minor neurological abnormalities or a family history of obscure early onset neurological disease. The different clinical pictures in the two affected siblings in this family suggest that MELAS syndrome is part of a spectrum of inherited mitochondrial cytopathies rather than a discrete disease entity.

Acidosis, Lactic↗
PubMed1988

Biochemical defects in mitochondrial cytopathies: a new classification.

Current classifications of mitochondrial cytopathies neglect rigorous assessment of the literature which consists often of single case reports. In addition no attempt is made by many workers to distinguish between primary and secondary respiratory chain defects. Current biochemical classifications also fail to take into account the considerable number of patients who have ragged red fibre myopathies and lactic acidosis but who do not show demonstrable respiratory enzyme defects. For this reason a new approach is advocated with consideration of possible respiratory chain defects, probable primary respiratory chain defects, probable secondary respiratory chain defects, and mitochondrial cytopathies with normal respiratory chain enzyme function in vitro. Existing knowledge is reviewed under these categories to which are added further original observations.

Animals↗
PubMed1988

Thyroid screening in elderly hospital patients.

A screening programme of thyroid disease in 214 elderly patients attending hospital was undertaken incorporating clinical and biochemical assessment. The prevalence of untreated hypothyroidism was 2.8%, treated hypothyroidism 2.8%, untreated hyperthyroidism 0.9%, sub-clinical hypothyroidism 4.7%, and non-thyroidal illness 3.3%. One patient with hypopituitarism was identified. Clinical judgement alone was poor. The costs of such a screening programme are discussed and the benefits highlighted.

Aged↗
PubMed1987

Chronic alcoholic proximal wasting: physiological, morphological and biochemical studies in skeletal muscle.

Electromyography, muscle histochemistry and assay of all glycolytic enzymes, phosphorylase, glycogen, carnitine and several mitochondrial marker enzymes in skeletal muscle (vastus lateralis) were carried out in two groups. One group comprised chronic alcoholic patients with prominent proximal wasting, the other was an alcoholic group with normal neuromuscular examination. Biochemical results were compared with data from control groups with normal muscle histology and with non-alcohol related type 2b fibre atrophy. Either 2b atrophy factor or 2b variability coefficient were increased in all wasted alcoholic patients, with normal values in alcoholics without wasting. Electromyography studies were usually normal in proximal muscles, although several patients had mild distal neuropathies. A significant fall in activity of phosphorylase and all glycolytic enzymes was found in wasted alcoholics with reference to normal controls. In the non-ethanolic 2b atrophy group the activity of several glycolytic enzymes was also significantly lower, but for each enzyme the mean activity was not depressed to the same extent as in the wasted alcoholic group. Muscle glycogen, carnitine, and mitochondrial marker enzyme activities (isocitrate dehydrogenase, monoamine oxidase, cytochrome oxidase) were normal in alcoholics with proximal wasting. It is concluded that there is no deficiency of mitochondrial marker enzymes in wasted alcoholics and that a significant depression in glycogenolytic and glycolytic enzyme activity is seen which is explained in part, but probably not fully, by 2b fibre atrophy.

Adult↗
PubMed1987

Extended neuralgic amyotrophy syndrome.

Neuralgic amyotrophy refers to an idiopathic syndrome where weakness and wasting occur in one limb, usually in the muscles innervated by the upper brachial plexus. Seven patients are presented who developed cranial nerve involvement (facial, spinal accessory) in the midst of a typical attack of neuralgic amyotrophy or who developed either recurrent brachial or brachial and lumbosacral plexopathies. An underlying demyelinating neuropathy was identified in one patient and two patients were herion addicts. These reports confirm that neuralgic amyotrophy may occasionally form part of a more extensive disorder of the peripheral nervous system, thereby providing indirect support for the role of a systemic immunological factor in pathoetiology.

Adult↗
PubMed1987

Chronic fatigue and myalgia syndrome: mitochondrial and glycolytic studies in skeletal muscle.

Clinical and biochemical findings in skeletal muscle in 11 patients with chronic fatigue myalgia syndromes of unknown aetiology are reported. All patients had severe asthenia for from one to 10 years with greatly limited exercise capacity and protracted exhaustion after minor exercise. Diffuse myalgia was prominent and was exacerbated for hours to days after exercise. Assay of skeletal muscle carnitine, phosphorylase, all glycolytic enzymes and the mitochondrial marker enzymes monoamine oxidase, isocitrate dehydrogenase and cytochrome oxidase were normal. These findings lend no support to the presence of a major defect in muscle intermediary energy pathways in this syndrome.

Adult↗
PubMed1987

Mitochondrial studies in Kearns-Sayre syndrome: normal respiratory chain function with absence of a mitochondrial translation product.

Intact mitochondria were isolated from skeletal muscle of two patients with Kearns-Sayre syndrome (retinitis pigmentosa, heart block, chronic external ophthalmoplegia), and mitochondrial protein translation was measured. Mitochondrial protein synthesis was up to 10 times greater than in control subjects and SDS-polyacrylamide gel electrophoresis revealed absence of a translation product with the mobility of a 5 KDa protein. State 3 respiration rates were normal with site 1 and site 2 substrates, suggesting that the absent protein was not a functional subunit of a respiratory chain complex.

Adult↗
PubMed1987

Spinal arteriovenous malformations: some diagnostic difficulties with illustrative cases.

Spinal arteriovenous malformations commonly present with progressive or step-like cord and conus dysfunction. Diagnosis is achieved by demonstrating abnormal vessels on the cord by means of high-quality myelography followed by selective spinal angiography. Diagnostic difficulties arise where screening myelography is equivocal or where angiography is negative in patients with suggestive myelographic findings. Negative investigation may not exclude a spinal arteriovenous malformation in patients with very suggestive clinical presentations. Occasionally reinvestigation after a period of follow-up or surgical exploration, even in the absence of a definite diagnosis, may be indicated.

Arteriovenous Malformations↗
PubMed1987

Relapsing eosinophilic myositis--a cause of pseudothrombophlebitis in an alcoholic.

A 51-year-old chronic alcoholic man presented with recurrent calf and thigh swelling and was investigated on several occasions for possible deep venous thrombosis. The episodes were precipitated by binge drinking. Muscle biopsy was performed on 3 occasions, revealing an inflammatory myopathy. On one of these occasions eosinophils were prominent in the interstitial infiltrate. Eosinophilic infiltrates in skeletal muscle may be a transient phase of the cellular process in the inflammatory myopathy and perhaps do not denote a specific nosological entity.

Alcoholism↗
PubMed1986

Dominantly inherited cardioskeletal myopathy with lysosomal glycogen storage and normal acid maltase levels.

A family is presented in which 7 members over 3 generations were affected by cardioskeletal myopathy. A vacuolar myopathy with excessive free and intralysosomal glycogen storage in skeletal and cardiac striated muscle was identified in biopsy studies. Post-mortem studies in several patients revealed changes of a congestive cardiomyopathy with myocardial fibrosis. Acid maltase, phosphorylase, debrancher and lysosomal enzyme screens, and glycolytic enzyme levels in skeletal muscle, were normal in 1 case. This is the third report of non-acid maltase deficient lysosomal glycogen storage disease and adds to previous reports with the presentation of detailed family studies, examined of ante- and post-mortem cardiac histology and reports of detailed glycolytic and lysosomal enzyme analysis. This syndrome is unusual among glycogenoses in having a dominant inheritance pattern.

Adult↗
PubMed1986

Cryoglobulinaemic neuropathy--a clinical spectrum.

In this report we present two cases who illustrate both ends of the spectrum of neuropathy with cryoglobulinaemia. Both patients responded well to treatment. A cryoglobulin assay should be done routinely in patients with mononeuritis multiplex of unknown cause, cutaneous vasculitis with cold sensitivity and chronic demyelinating neuropathies of unknown cause.

Adult↗
PubMed1985

Experimentally induced defects of mitochondrial metabolism in rat skeletal muscle. Biological effects of the mitochondrial uncoupling agent 2,4-dinitrophenol.

Infusion of dinitrophenol intra-arterially into rat hind limb caused an irreversible failure of isometric twitch tension and the induction of a severe progressive contracture. Metabolite analysis of muscle in which the twitch response had grossly fatigued revealed low levels of ATP and phosphocreatine together with lactate accumulation. Studies using 31P-n.m.r. confirmed the decrease in ATP and creatine phosphate concentrations and indicated a fall in intracellular pH. It is concluded that dinitrophenol-induced myopathy does not represent a good model for the human mitochondrial myopathic condition as has been previously suggested.

2,4-Dinitrophenol↗
PubMed1985

Experimentally induced defects of mitochondrial metabolism in rat skeletal muscle. Biological effects of the NADH: coenzyme Q reductase inhibitor diphenyleneiodonium.

An animal model for the human condition of mitochondrial myopathy has been established and characterized physiologically and biochemically. The NADH: coenzyme Q reductase inhibitor diphenyleneiodonium [Bloxham (1979) Biochem. Soc. Trans. 7, 103-106] was either infused acutely in vivo into rat hind limb or injected chronically into rats. Both modes of delivery resulted in a reduced muscle oxidative capacity and increased fatigue. Analysis of muscle metabolites by h.p.l.c. and 31P-n.m.r. indicated that ATP concentrations were similar to control values during periods of stimulation and these were maintained by the phosphocreatine pool. During the recovery period after muscle stimulation in the experimental animals the muscle pH remained depressed and the rate of phosphocreatine synthesis was markedly delayed as compared with controls. Factors thought to be involved in the fatigue response are discussed in relation to this model.

Animals↗