摘要:

Cultured fibroblasts from 13 patients with organic aciduria suggesting 3-oxothiolase deficiency were studied by measuring first the capacity of the isoleucine degradative pathways in whole cells, as the incorporation of l-[14C]-2-methylbutanoic acid into macromolecules, and, second, the activity of 3-oxothiolase in cell homogenates using specific 3-oxoacyl-CoA substrates to identify the different enzymes. Nine patients showed low incorporation by the macromolecular labeling assay, as well as deficiency of 2-methylacetoacetyI-CoA thiolase. In this group of patients, low activity by the macromolecular labeling assay was associated with clinically severe symptoms, and vice versa. Two patients showed reduced macromolecular labeling, but apparently normal 3-oxothiolase. Finally, two patients showed normal activities by either test, the reason for their particular organic aciduria being unknown. In conclusion, occurrence of urinary 2-methyl-3-hydroxybutyric acid and/or tiglylglycine is not an unequivocal indicator of the absence of the thiolase that metabolizes 2-methylacetoacetyl-CoA. Measurement of l-[l4C]-2-methylbutanoic acid incorporation in cultured fibroblasts adds important information in studying possible defects of the isoleucine catabolic pathway.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

A number of neuromuscular diseases are associated with molecular defects in the mitochondrial DNA (mtDNA). These include: 1) a missense mutation at nucleotide 11778 in the mtDNA of Leber's hereditary optic neuropathy patients; 2) a heterogeneous array of deletions in the mtDNA of ocular myopathy patients; and 3) small deletions and point mutations in the mtDNA of myoclonic epilepsy and ragged red fiber disease patients. We can now diagnose these diseases at the molecular level from small patient samples by amplifying the affected mtDNA regions using the polymerase chain reaction. Leber's hereditary optic neuropathy is diagnosed through loss of an SfaNI restriction site. Ocular myopathy deletions are identified by differential amplification across deletion breakpoints. Familial diseases such as myoclonic epilepsy and ragged red fiber disease might be diagnosed by identifying small deletions through amplification and electrophoretic analysis of the entire mtDNA genome or by identifying point mutations through differential oligonucleotide hybridization. As additional mtDNA molecular defects are identified, molecular analysis will likely become a primary tool for the diagnosis of these diseases.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

We have reviewed the structure, function, and biogenesis of mammalian cytochrome c oxidase, examined the tissue-specific expression of isoforms of cytochrome c oxidase subunits in different mammals, and attempted to correlate the data with our knowledge of cytochrome c oxidase deficiency, illustrated by one particular patient. Cytochrome c oxidase was isolated from bovine tissues, and individual subunits examined by SDS-PAGE, N-terminal peptide sequencing, and antibody binding. Isoforms of subunits VIa, VIIa, and VIII were identified, manifesting one pattern of expression in heart and skeletal muscle, and another in liver, kidney, and brain. In rat heart and liver, only one form of subunit VIIa was identified. Northern analysis of bovine and rat tissues suggested that the tissue-specific expression of subunits VIa and VIII is regulated transcriptionally in liver, kidney, and brain, and posttranscriptionally in heart and skeletal muscle. In humans, antibody binding documented isoforms of subunits VIa and VIIa, with the pattern of expression in heart and skeletal muscle differing from that in liver, kidney, and brain; our data suggested that both isoforms of subunit VIa may be expressed in human heart. In a patient with cytochrome c oxidase deficiency, the clinical, morphologic, and biochemical manifestations were much more severe in heart than in skeletal muscle. Antibody binding suggested partial assembly of the enzyme in heart. These and other data suggest considerably more variability in the tissue-specific expression of isoforms of cytochrome c oxidase subunits than previously recognized

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Cytochrome c oxidase (COX) is a complex enzyme composed of 13 subunits, three of which are encoded by the mitochondrial DNA (mtDNA). The other 10 subunits are encoded by the nuclear DNA, synthesized in the cytoplasm, and transported into the mitochondria. The complexity of the enzyme and its dual genetic control explain the heterogeneity of clinical phenotypes associated with COX deficiency. There are two major syndromes, one characterized by muscle involvement (fatal infantile or benign infantile myopathy), the other dominated by brain disease (Leigh syndrome, myoclonic epilepsy with ragged red fibers, Menkes' disease). Partial defects of COX have been shown in muscle of patients with progressive external ophthalmoplegia, either alone (ocular myopathy) or as part of Kearns-Sayre syndrome. Biochemical studies have documented either muscle-specific or generalized defects of COX; COX deficiency is reversible in the benign infantile myopathy. Immunologically detectable protein may be normal (benign myopathy) or variably decreased (fatal myopathy, Leigh syndrome). The subunit pattern of COX is normal by immunoblot in patients with fatal myopathy and Leigh syndrome; a disproportionate decrease of subunit II was seen in a patient with myoclonic epilepsy with ragged red fibers. Availability of the three mtDNA genes and of complementary DNA probes for eight of the 10 nuclear DNA-encoded subunits makes it possible to investigate the different diseases at the molecular level. Large deletions of mtDNA have been found in patients with ocular myopathy and Kearns-Sayre syndrome: the deleted mtDNA appear to be transcribed but not translated, thus explaining the partial COX deficiency.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Chronic progressive external ophthalmoplegia (CPEO) describes a recognizable clinical syndrome frequently associated with variable dysfunction in other organ systems. Histochemical and biochemical studies suggested primary dysfunction of oxidative phosphorylation. This has recently been confirmed by demonstration of partially deleted as well as normal mitochondrial DNA— heteroplasmy—in some of these patients, most of them sporadic. In the six heteroplasmic CPEO patients that we have examined to date, the partially deleted species has been detected in all tissues tested, albeit in vastly different proportions. We report here detection of physiologically significant proportions of partially deleted mitochondrial DNA in several organs taken at autopsy from a CPEO patient with severe multisystem disease. We discuss the relationship of CPEO to several other clinical phenotypes associated with mitochondrial dysfunction, and discuss the possible implications of heteroplasmy for the development of variable phenotypes.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Cultured skin fibroblasts from patients with lacticacidemia were incubated with glucose for 1 h and the lactate and pyruvate production measured. Those patients with increased lactate to pyruvate ratios were further analyzed for the cause of the abnormal redox state. Two categories of patients are described. The first contains patients with either severe or partial cytochrome oxidase deficiency; this group can be broken down further into patients with Leigh's disease, Kearns-Sayre syndrome, and liver-specific cytochrome oxidase deficiency. In this group, the rise in lactate to pyruvate ratio roughly correlated with the severity of the defect. The second patient category had defects located in complex I of the mitochondrial respiratory chain. This is easily demonstrated in the most severely affected patients with the fatal infantile form of the disease. Patients with severe defects in either complex I or cytochrome oxidase had complexes that were only partially assembled. Patients with mitochondrial encephalopathy with lactic acidosis and stroke-like episodes demonstrated only minor changes in redox state and in the behavior of the mitochondrial respiratory chain.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID