We investigated the correlations of deletions of mitochondrial DNA in skeletal muscle with clinical manifestations of mitochondrial myopathies, a group of disorders defined either by biochemical abnormalities of mitochondria or by morphologic changes causing a ragged red appearance of the muscle fibers histochemically. We performed genomic Southern blot analysis of muscle mitochondrial DNA from 123 patients with different mitochondrial myopathies or encephalomyopathies. Deletions were found in the mitochondrial DNA of 32 patients, all of whom had progressive external ophthalmoplegia. Some patients had only ocular myopathy, whereas others had Kearns-Sayre syndrome, a multisystem disorder characterized by ophthalmoplegia, pigmentary retinopathy, heart block, and cerebellar ataxia. The deletions ranged in size from 1.3 to 7.6 kilobases and were mapped to different sites in the mitochondrial DNA, but an identical 4.9-kilobase deletion was found in the same location in 11 patients. Biochemical analysis showed decreased activities of NADH dehydrogenase, rotenone-sensitive NADH-cytochrome c reductase, succinate-cytochrome c reductase, and cytochrome c oxidase, four enzymes of the mitochondrial respiratory chain containing subunits encoded by mitochondrial DNA. We conclude that deletions of muscle mitochondrial DNA are associated with ophthalmoplegia and may result in impaired mitochondrial function. However, the precise relation between clinical and biochemical phenotypes and deletions remains to be defined.

The cerebro-hepato-renal syndrome is a rare familial malady with cerebral, renal, and skeletal abnormalities, severe hypotonia, cirrhosis, iron and lipid storage, and death within 6 months. Correlated electron microscopic, histochemical, and biochemical studies demonstrate defects in two oxidative organelles. Peroxisomes cannot be found in hepatocytes and renal proximal tubules. In hepatocytes and cortical astrocytes, mitochondria are distorted in their appearance and glycogen stores are increased. Oxygen consumnption of brain and liver mitochondrial preparations with succinate and with substrates reducing nicotinamide adenine dinucleotide is markedly diminished, but the consumption is normal with ascorbate and tetramethylphenylenediamine, which suggests a defect in electron transport prior to the cytochromes. Histochemical studies of mitochondrial oxidation point to a defect between the succinate dehydrogenase flavoprotein and coenzyme Q, possibly in the region of nonheme iron protein.

FOR SEVERAL WEEKS prior to the formation of mature muscle cells, the process of which is virtually completed by the fifth fetal month in humans,1 the cell exists as a myotube. Similar muscle cells were seen in the biopsy of an adolescent boy with a muscle-wasting disorder.Since this unusual pathological occurrence appears to be unique, it is the purpose of this report to present the clinical, pathological, cytochemical, and electron microscopic studies of this disease. An attempt will also be made to correlate these findings with previously reported studies in myogenesis. MethodsBiopsy specimens of gastrocnemius muscle were removed on two separate occasions (September 1962 and January 1965) after infiltration of the overlying skin with a local anesthetic. The initial specimen was removed with sutures and fixed in Zenker's solution; the second specimen was removed with a C-shaped clamp designed for that purpose, and fixed in Bouin's solution. Both specimens were oriented in a manner whereby both cross and longitudinal sections could be made. The fixed sections from the first biopsy were stained with hematoxylin and eosin. In addition to this, the sections from the second biopsy were stained with the hematoxylin-van Gieson, Gomori trichrome, periodic acid-Schiff (PAS) and Lillie allochrome techniques.2 During the second biopsy, a muscle specimen was frozen in isopentane cooled to \p=m-\160 C by liquid nitrogen. Thin sections cut in a cryostat were stained unfixed for histochemical and cytochemical studies. Sections were stained with the modified Gomori trichrome technique for morphological de¬ tail.3 Mitochondrial oxidative enzymatic activity and enzymes involved in electron transport were studied with the cytochrome oxidase,1 nicotinamide adenine nucleotide dehydrogenase (NADH),5 and succinic dehydrogenase (SDH) reactions." Myofibrillary activity was sudied using adenosine triphosphatase (ATPase).7 Individual sarcoplasmic contents were studied utilizing amylophosphorylase and the periodic acid-Schiff stain.Lipids were stained using scharlach-R and Sudan black. Sections were also stained for acid phosphatase.8 Immunofluorescence studies were done using rabbit anti-human myosin and fluorescein labelled anti-rabbit globulin.8 Electron Microscopy.-For electron microscopy, tissue immediately frozen at -160 C in liquid nitrogen and stored at -4 C for four weeks was thawed at room temperature and fixed in 1'% osmium tetroxide in barbital (Veronal) acetate buffer10 for two hours. Dehydration was carried on in ascending solutions of acetone, and English Araldite * was used for embedding. A microtome was used for sectioning of the blocks. The sections were examined in an electron microscope.A 12-year-old white boy was admitted to Chil¬ dren's Hospital of Philadelphia in January 1965 for evaluation of muscle weakness and repeat muscle biopsy. This was prompted by uniquely abnormal fibers found in routine review of the patient's muscle biopsy done in 1962.This boy (Fig 1) was the product of his then 30-year-old mother's fifth...

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