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Biomedical subjects

O B Evans

Publications and source records attributed to O B Evans.

At least 37 records · Page 2Linked to original sources
PubMed1984

Glycogen-membrane complexes in denervated human skeletal muscle.

We describe an unusual intracellular complex of glycogen with smooth, cisternal, cytoplasmic membranes (glycogen-membrane complexes, GMC) in denervated human skeletal muscle. Glycogen particles were always intimately associated with these structures, although the staining intensity varied markedly with different fixation conditions. This may account for previous investigations of similar structures in which an association with glycogen was not recognized. Electron micrographs of tannic acid-enhanced specimens, and of freeze-fracture replicas, showed similarities between the GMCs and the terminal cisternae of the sarcoplasmic reticulum: (i) GMCs resembled the terminal cisternae of the sarcoplasmic reticulum in the size and asymmetric distribution of intramembranous particles seen in freeze-fracture replicas; (ii) tannic acid-enhanced thin sections of GMCs showed intense staining of the cisternal contents and irregular staining of the cytoplasmic leaflet, similar to the appearance of the sarcoplasmic reticulum terminal cisternae; and (iii) triad-like junctions were seen between the glycogen-membrane complexes and elements of the transverse tubule system.

Cell Membrane↗
PubMed1984

Ischemia of the brain stem as a cause of sudden infant death syndrome.

Recent evidence indicates that the sudden infant death syndrome (SIDS) is related to abnormal control of respiration. Focal morphologic changes have not been noted. In a case of SIDS, ischemic degeneration was noted bilaterally in the medulla, particularly in the dorsal motor nucleus of the vagus nerve. Pathologic changes were not found elsewhere in the CNS. To our knowledge, this is the first description of a focal brain-stem lesion in SIDS that had enough of a role in altered respiratory control to cause death.

Brain Ischemia↗
PubMed1983

Muscle pyruvate oxidation following denervation and reinnervation.

Muscle pyruvate metabolism was studied in rats following sciatic nerve crush. Control studies showed high pyruvate dehydrogenase and lipoamide dehydrogenase enzyme activity in muscle with type 1 fiber predominance (soleus) and low activities in muscle with type 2 fiber predominance (extensor digitorum longus), whereas lactate dehydrogenase was much higher in the latter. Following denervation, both muscles showed a significant reduction in pyruvate dehydrogenase enzyme activity. During reinnervation, muscle with type 2 predominance developed significantly elevated pyruvate oxidation enzyme activities.

Animals↗
PubMed1983

Effects of dichloroacetate on brain tissue pyruvate dehydrogenase.

The activation of the pyruvate dehydrogenase complex (PDHC) by dichloroacetate (DCA) was studied in brain tissue. Chronic administration of DCA to rats caused no significant change of PDHC activation in brain. DCA brain concentrations were comparable to those of other tissues in which activation is known to occur. No effect of DCA on PDHC could be demonstrated from isolated brain mitochondria, whereas DCA reversed the deactivation of PDHC by ATP, alpha-ketoglutarate plus malate, and succinate in liver mitochondria. This study suggests that the regulation of PDHC activation in neural tissue differs from that in other tissues.

Acetates↗
PubMed1983

Improvement of muscle function in acid maltase deficiency by high-protein therapy.

Progressive muscle weakness in acid maltase deficiency (AMD) is associated with intralysosomal accumulation of glycogen and altered myofibrillar morphology. A rapid fall in circulating branched chain amino acids after protein ingestion in a child with AMD suggested that increased net muscle protein catabolism may play a part in the pathogenesis of this condition. To reduce this muscle catabolism, the patient was treated with a high-protein diet for 12 months. This has reversed the weakness and wasting, with improvement in muscle function, exercise tolerance, and growth.

Amino Acids, Branched-Chain↗
PubMed1983

Human muscle pyruvate dehydrogenase activity.

Muscle pyruvate dehydrogenase complex (PDHC) activity was studied in 70 patients with different neuromuscular disorders. Children had higher total PDHC and lipoamide dehydrogenase (LAD) activities than adults. There were no significant differences in muscle PDHC activity in patients with Friedreich ataxia, patients with other ataxias, or age-matched controls. Kinetic analysis of LAD showed no differences in Km for lipoamide between Friedreich ataxia patients and controls.

Adolescent↗
PubMed1982

Dichloroacetate tissue concentrations and its relationship to hypolactatemia and pyruvate dehydrogenase activation.

Following a single oral dose of DCA to laboratory rats, peak hepatic tissue DCA concentration occurred at 3 hr. When given chronically for 7 days, DCA caused activation of the pyruvate dehydrogenase complex which returned to basal activity 24 hr following the final dose. Hepatic tissue DCA concentrations were maximally increased at 3 hr following the final dose, and the drug was eliminated slowly over 72 hr with a half-life of 9.74 hr. Liver and muscle showed similar DCA tissue concentrations following chronic administration.

Acetates↗
PubMed1982

Prolonged hypolactatemia and increased total pyruvate dehydrogenase activity by dichloroacetate.

Dichloroacetate (DCA) given gastrically as a single dose to healthy, fed rats caused transient lowering of blood glucose, lactate, and pyruvate. Chronic daily dosing caused lowering of these metabolites and a delay in the return of lactate to basal levels for 48 hr after the final dose. DCA caused activation of the pyruvate dehydrogenase complex (PDHC), with acute multiple dosing or chronic daily dosing. The elevated active PDHC persisted for 12 hr following the final dose. In addition, total PDHC activity was increased with chronic dosing and persisted for 48 hr following the final dose. This increase was not blocked by protein synthesis inhibitors. DCA increased isolated hepatocyte [14C-1]pyruvate oxidation and activated hepatocyte PDHC. Glyoxylate and oxalate, hepatic metabolites of DCA, were inhibitory at similar concentrations.

Acetates↗
PubMed1982

Reversal of debrancher deficiency myopathy by the use of high-protein nutrition.

A child with debrancher deficiency presented with myopathy, recurrent hypoglycemia, and growth failure. Evidence for enhanced gluconeogenesis was demonstrated by low postabsorptive gluconeogenic plasma amino acids, a marked fall in alanine during fasting, and a substantial rise in plasma glucose following protein ingestion. The patient was treated with high-protein nocturnal intragastric therapy, which resulted in marked improvement in exercise tolerance, muscle strength and mass, electromyographic findings, and growth.

Amino Acids↗
PubMed1982

A new familial disorder of combined lower motor neuron degeneration and skeletal disorganization.

A new familial disorder, inherited as an autosomal dominant trait and characterized by dual features of neurologic degeneration and skeletal disorganization, is reported. The neurologic disease is a degenerative process of lower motor neurons and develops in middle age with progressive muscle weakness and ends in respiratory failure and premature death. Clinical examination, electromyography, and muscle biopsy with histochemical stains are diagnostic. The skeletal disorganization resembles Paget's disease of bone. It is characterized by polyostotic radiographic abnormalities, elevated serum alkaline phosphatase of bone origin, abnormal radioisotopic bone scan, elevated hydroxyprolinuria, and bone histology.

Age Factors↗
PubMed1981

Pyruvate decarboxylase deficiency in subacute necrotizing encephalomyelopathy.

A partial deficiency of pyruvate decarboxylase (PDC) was demonstrated in a child with hyperlactatemia and progressive ataxia, bulbar paresis, ophthalmoplegia, and polyneuropathy. Subacute necrotizing encephalomyelopathy (SNE) was found at necropsy. The association of SNE and PDC deficiency has been reported rarely, but a review of the diverse metabolic defects associated with SNE suggests that decreased PDC activity may be the common feature of SNE.

Alanine↗