Search PubMed⌕ Search

Biomedical subjects

S DiMauro

Publications and source records attributed to S DiMauro.

At least 361 records · Page 20Linked to original sources
PubMed1979

Debrancher deficiency: neuromuscular disorder in 5 adults.

Five patients, 4 men and 1 woman, had adult-onset and slowly progressive weakness. There was distal wasting in 2, hepatomegaly in 3, and congestive heart failure in 2. Electromyography showed a mixed pattern with abundant fibrillations. Serum creatine phosphokinase was increased 5- to 45-fold. Blood glucose failed to respond to epinephrine or glucagon, and venous lactate did not rise after ischemic exercise. Muscle biopsy showed vacuolar myopathy affecting both fiber types. By electron microscopy the vacuoles corresponded to large pools of glycogen not limited by a membrane. Glycogen concentration was 3 to 5 times normal in muscle and 7 to 21 times normal in erythrocytes. In the presence of iodine, muscle glycogen showed a spectrum characteristic of phosphorylase-limit-dextrin. Debrancher activity was measured by a spectrophotometric assay and by a radioactive reverse reaction. The activity was lacking in muscle and erythrocytes of 4 patients according to both assays; in 1 patient the reverse reaction was not impaired. Though previously reported in only 5 patients, debrancher deficiency myopathy may not be rare and should be considered in the differential diagnosis of adult-onset hereditary myopathies.

Adolescent↗
PubMed1979

Muscle carnitine deficiency. Genetic heterogeneity.

Two types of lipid storage myopathy have been associated with decreased content of carnitine in muscle. In "muscle carnitine deficiency", carnitine concentration is normal in serum, but reduced in muscle. In "systemic carnitine deficiency", apparently due to imparied synthesis of carnitine in the liver, carnitine content is low in both serum and muscle. We studied a woman with a corticosteroid-responsive, probably autosomal recessive, lipid storage myopathy. Carnitine therapy was ineffective and carnitine failed to correct the impaired fatty acid oxidation in muscle homogenates, in contrast to a previous case. Carnitine transport into skeletal muscle was normal. These observations suggest that ll cases of "muscle carnitine deficiency are not the same.

Adult↗
PubMed1979

Phosphorylase isoenzymes in normal and myophosphorylase-deficient human heart.

Phosphorylase isoenzymes were studied by acrylamide-slab electrophoresis in normal tissues and in the heart of a child with a fatal infantile form of myophosphorylase deficiency. Of the three bands present in normal human heart, two were missing in the patient's heart: the slow "muscle" isoenzyme and the intermediate band. Only the fast "cardiac" isoenzyme remained. When extracts of normal skeletal muscle and the patient's heart were mixed in appropriate conditions, the intermediate band reappeared in the electropherogram. Phosphorylase activity in extracts of the patient's heart was not inhibited by antibodies against purified enzyme from mature human muscle, whereas normal human heart phosphorylase was inhibited by approximately 50%. These results suggest that the intermediate band of human heart phosphorylase is a hybrid of skeletal and cardiac muscle isoenzymes. Retained activity of the cardiac isoenzyme may explain why patients genetically lacking skeletal muscle phosphorylase do not have clinical heart disease.

Adolescent↗
PubMed1978

McArdle disease: the mystery of reappearing phosphorylase activity in muscle culture--a fetal isoenzyme.

To understand the apparently paradoxical appearance of phosphorylase in muscle cultured from patients with McArdle disease, the enzyme in muscle culture was studied immunologically and electrophoretically. Antibody against normal human muscle phosphorylase completely inhibited the enzyme of adult muscle, but it had no effect on phosphorylase activity of muscle cultures from normal individuals or patients with McArdle disease. Also, amounts of antibody that would completely inhibit phosphorylase in mature muscle left about 30% of the activity in muscle obtained from human fetus at four months' gestation. Acrylamide-disc and slab-gel electrophoresis showed a single band of phorphorylase activity in adult muscle and two bands in fetal muscle. This suggested that at four months' gestation, both fetal and mature forms are present but that only the mature isoenzyme is inhibited by the antibody. The enzyme from cultured muscle gave only a single band, with the electrophoretic mobility of the fetal isoenzyme. These data suggest that phosphorylase activity in muscle cultured from patients with McArdle disease is due to a fetal isoenzyme whose genetic control is different from that of the mature enzyme.

Antibody Formation↗
PubMed1978

Studies of fragmented sarcoplasmic reticulum from human skeletal muscle.

Sarcoplasmic reticulum (SR) vesicles were isolated from muscle biopsies of 4 normal volunteers, a patient with McArdle disease (before and during contracture), and a patient with normokalemic periodic paralysis. Fractions were analyzed for purity by electron microscopy and biochemical analysis of specific marker enzymes. Adenosine triphosphate (ATP)-dependent calcium ion uptake was measured kinetically by the absorbence changes of murexide, a metallochromic indicator of ionized Ca++ concentrations, in the absence of oxalate or other calcium-complexing anions. In these experiments, time resolution of the Ca++ transport rate was limited by the manual mixing of reagents, which occurred in 1 to 3 seconds. In 1 case the "true" initial velocity of Ca++ uptake was measured by rapid mixing of ATP in a stopped-flow apparatus and by following the change in absorbence of murexide in a storage oscilloscope. In SR from normal human muscle the ATP-dependent Ca++ uptake was 3.5 nmoles per second per milligram of protein for the first 5 seconds after ATP mixing. Fast kinetic experiments showed that Ca++ uptake proceeded linearly for the first 500 msec at a rate of 9 nmoles per second per milligram of protein (at 25 degrees C) and then progressively declined to reach steady-state levels in 40 to 50 seconds. No abnormality of Ca++ transport was found in SR vesicles from the patient with McArdle disease and the patient with normokalemic periodic paralysis.

Adenosine Triphosphatases↗
PubMed1978

Tissue carnitine in Reye syndrome.

Skeletal muscle carnitine palmityltransferase and muscle or liver carnitine content were determined in biopsies from children during and after attacks of Reye syndrome. No consistent abnormality of enzyme or cofactor was found. Reye syndrome is biochemically distinct from the clinically similar syndrome of systemic carnitine deficiency.

Acyltransferases↗
PubMed1978

Fatal infantile form of muscle phosphorylase deficiency.

A girl had generalized, rapidly progressive weakness beginning at age 4 weeks, and causing severe respiratory insufficiency and death at age 13 weeks. Histochemical and biochemical investigations of a muscle biopsy showed increased glycogen concentration and complete lack of phosphorylase activity. The enzyme protein appeared to be absent by immunodiffusion, and the metabolic block was documented by studies of anaerobic glycolysis in vitro. The biochemical basis for the unusual clinical picture is obscure, but muscle phosphorylase deficiency has to be considered in the differential diagnosis of the "floppy baby syndrome".

Female↗
PubMed1977

Carbohydrate metabolism in hypothyroid myopathy.

The carbohydrate metabolism in hypothyroid patients was investigated. After an overnight fast, the blood glucose level was 24% lower and the blood lactate level was 35% lower in the untreated hypothyroid patients than that observed in the treated hypothyroid patients or in the normal subjects. There was no difference in the blood alanine or plasma free fatty acid values between the subject groups. Skeletal muscle biopsied from two hypothyroid patients with marked myopathy showed normal glycogen content, 0.83%-0.86% (normal 1.06%), but reduced activity of acid maltase, 32-50 nmoles/min/g (normal 97). Forearm ischemic stimulation applied to hypothyroid patients failed to elevate the level of lactate. The results are compatible with impaired glycogenolysis from the skeletal muscle, which may be a contributory factor in the myopathy in hypothyroidism.

Adolescent↗
PubMed1977

Residual acid maltase activity in late-onset acid maltase deficiency.

Residual acid maltase activity was found by a sensitive fluorometric assay in muscle biopsies from 15 patients with late-onset acid maltase deficiency (mean, 6.91 percent; range, 2.4 to 12.2) but not in biopsy or autopsy muscle from three patients with the infantile form. Electrophoresis, kinetic characteristics, and subcellular fractionation indicated that the residual activity was lysosomal acid maltase and not a contaminating isozyme of neutral maltase. There was no correlation between the amount of residual acid maltase activity and the severity of the clinical picture or glycogen accumulation. The presence of acid maltase activity in muscle, liver, and, to a greater extent, leukocytes in late-onset but not infantile acid maltase deficiency and the failure of the two disease forms to occur in the same family suggest that they are genetically distinct.

Adult↗
PubMed1976

Adult-onset acid maltase deficiency. Morphologic and biochemical abnormalities reproduced in in cultured muscle.

We established muscle-tissue cultures from biopsy of a patient with adult-onset acid maltase deficiency. Morphologically and biochemically, the newly grown fibers of the cultured muscle showed the same abnormalities as those of the biopsied muscle. Light microscopy showed multiple vacuoles filled with acid-phosphatase-positive material; on ultrastructural examination there was abnormal accumulation of glycogen in membrane-bound sacs (secondary lysosomes), some of which also contained dark membranous of homogeneous material. Acid maltase (pH 4.0), a lysosomal enzyme, was undetectable in either cultured or biopsied muscle by maltose hydrolysis, whereas acid phosphatase, also a lysosomal enzyme, was increased in both sources of muscle cells. Cultured muscle fibers demonstrate the same morphologic and biochemical abnormalities characteristic of biopsied muscle, supporting the concept of a biochemically distinct primary myopathy in man.

Acid Phosphatase↗
PubMed1976

Urinary excretion of carnitine in Duchenne muscular dystrophy.

The urinary excretion of carnitine by boys with Duchenne dystrophy did not differ significantly from age-matched controls. Since serum and muscle concentrations of carnitine are also normal in Duchenne dystrophy, it cannot be proved that this small molecule leaks from muscle in Duchenne dystrophy. If the muscle surface membrane is abnormally leaky in Duchenne dystrophy, different molecules seem to be affected in different ways.

Adolescent↗
PubMed1976

Neuromuscular disorder associated with a defect in mitochondrial energy supply.

A limb muscle biopsy specimen from a patient with a slowly progressive congenital neuromuscular disorder disclosed, by electron microscopy, widespread mitochondrial crystalline inclusions. Biochemical studies of isolated mitochondria showed decreased respiratory rate and respiratory control with both nicotine adenine dinucleotide and flavor-protein-linked substrates. Mitochondrial adenosine triphosphatase (ATPase) activity, both basal and magnesium (Mg++) or 2,4-dinitrophenol- (DNP) stimulated, was greatly reduced in contrast to normal. The rate and extent of mitochondrial calcium accumulation was normal. These findings are consistent with a defect of the respiratory chain-linked energy transfer at a level common to all three energy coupling sites of the respiratory chain. The defect in ATPase activity may be secondary to replacement of functional mitochondrial inner membrane by crystalline inclusions.

Adenosine Triphosphatases↗
PubMed1976

Late-onset acid maltase deficiency. Detection of patients and heterozygotes by urinary enzyme assay.

Daily urinary excretion of acid maltase (12.78 +/- 2.10 units/24 hr/mg of creatinine, in 11 normal adults) was significantly decreased in ten patients with late-onset acid maltase deficiency (1.33 +/- 0.16 units/24 hr; P less than .001) and 11 heterozygotes (3.27 +/- 0.62 units/24 hr; P less than .001). Maximal inhibition of urinary acid maltase activity by antibodies against human placental enzyme was 53% in controls, 30% in heterozygotes, and virtually absent in patients. Investigation of pH curves and enzyme inhibition by antibodies confirmed the presence in the kidney of an immunologically distinct "extra" maltase enzyme active at acid pH. Whether acid maltase in normal urine originates in the kidney or cells of the lower urinary tract, the enzyme defect seems to be expressed in these cells in late-onset acid maltase deficiency.

Adolescent↗
PubMed1976

Luft's disease. Further biochemical and ultrastructural studies of skeletal muscle in the second case.

In the second known case of non-thyroidal hypermetabolism (Luft's disease), there were large areas of mitochondrial aggregates in all fibers. Many mitochondria were abnormally large and contained packed cristae. In isolated mitochondrial fractions, studies of oxidative phosphorylation showed defective respiratory control and normal phosphorylation capacity ("loose coupling"). Spectra and content of cytochromes were normal. Basal ATPase activity was seven times greater than normal and poorly stimulated by 2,4-dinitrophenol. The rate of energy-dependent calcium uptake by isolated mitochondria was normal, but the amount of calcium accumulated was much decreased. Calcium could not be retained and was spontaneously released into the medium within 30 seconds. "Recycling" of calcium between mitochondria and cytosol may take place in vivo and result in sustained stimulation of respiration and loose coupling.

Adult↗