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Biomedical subjects

M H Brooke

Publications and source records attributed to M H Brooke.

At least 73 records · Page 4Linked to original sources
PubMed1981

Carnitine intake and excretion in neuromuscular diseases.

Free and total carnitine serum concentrations and urinary excretion were examined in patients with various neuromuscular diseases. On a measured, low carnitine diet and during fasting, the patients did not differ from controls. Carnitine excretion in patients (3.09 +/- 1.87 mumol/kg/day) and controls (2.99 +/- 1.12) exceeded carnitine intake (patients, 2.35 +/- 0.94 mumol/kg/day; controls, 1.33 +/- 0.70). Because of heterogeneity in the patient population, carnitine excretion was assessed according to creatinine excretion, chosen as an indicator of muscle mass. Those patients with daily creatinine excretion less than 1 g/day had significantly lower carnitine excretion (106 +/- 47 versus 205 +/- 95 mumol/day, p less than 0.05), and there was a positive correlation between creatinine excretion and carnitine excretion (r = 0.82) and between muscle carnitine and carnitine excretion (r = 0.67). Urinary clearances for acylcarnitine were 10 and 20 times higher than those for free carnitine. Two patients with carnitine palmityl transferase deficiency were similar to the other patients, but the carnitine-deficient patient lost excessive carnitine during fasting, probably secondary to elevated acylcarnitine fraction in the blood.

Adolescent↗
PubMed1981

Riboflavin-responsive lipid myopathy and carnitine deficiency.

We used riboflavin to treat a patient with lipid myopathy, reduced exercise capacity, intolerance to fasting, and reduced concentrations of carnitine in muscle and serum. Although carnitine concentrations did not change, exercise capacity doubled, and response to fasting improved. Muscle enzyme assay showed that palmityl CoA dehydrogenase activity with and without added flavin adenine dinucleotide (a riboflavin product) was normal. Another riboflavin derivative, electron transfer flavoprotein, could be the site of the defect.

Acyl-CoA Dehydrogenase↗
PubMed1980

Contractile, biochemical, and histochemical properties of thyrotoxic rat soleus muscle.

The effects of thyrotoxicosis on the contractile properties of soleus muscle were examined in rats given 3 mg of T4 and 1 mg of T3 per kg of diet for 6--8 wk. Thyrotoxicosis induced significant decreases in isometric twitch contraction time (CT), one-half relaxation time, and peak twitch tension. The Ca2+ uptake activity of the sarcoplasmic reticulum (SR) was increased in the thyrotoxic muscles; this adaptation in the SR provides a possible mechanism for the alterations in isometric contractile properties. Thyrotoxicosis induced a large increase in fibers classified as type 2, on the basis of an alkali-stable histochemical reaction for ATPase, in the soleus. Although this reaction is commonly interpreted as indicating that a muscle is fast, maximum shortening velocity (Vmax) and Mg2+ activated actomyosin ATPase activity were unaffected in the thyrotoxic soleus. Our findings provide evidence that CT and Vmax can vary independently and that the histochemical ATPase reaction may not always reflect the biochemical properties that make myosin fast or slow.

Adenosine Triphosphatases↗
PubMed1980

Endurance exercise training in a patient with central core disease.

A 36-year-old man with central core disease underwent endurance exercise training on a bicycle ergometer for 9 months. The training resulted in an increase in work capacity and maximal oxygen consumption of approximately 50%. Further improvement in his exercise capacity seemed limited by the primary disease. These results suggest that some neuromuscular disease patients may benefit from endurance exercise training.

Adult↗
PubMed1980

Carnitine "deficiency": lack of response to carnitine therapy.

A 29-year-old women had muscle weakness, low concentrations of carnitine in muscle and serum, and abnormally low urinary excretion of carnitine. During a fast, exercise capacity declined, ketone body concentrations rose, metabolic acidosis worsened, and she became hypoglycemic. After treatment with oral carnitine, serum carnitine content returned to normal and blood glucose was maintained during fasting, but ketone body concentrations in blood were even higher. Muscle carnitine content and exercise capacity did not improve. This patient demonstrated features of both systemic and muscle carnitine deficiency, suggesting that the current classification of carnitine-deficiency syndromes is inadequate.

Adolescent↗
PubMed1979

Bicycle ergometry and gas exchange measurements in neuromuscular diseases.

Using bicycle ergometry with computerized respiratory gas exchange measurements, we compared exercise capacities in patients with various neuromuscular diseases to those in normal controls. As expected, male and female patients had significantly reduced maximum work capacities (kilopond-meters per minute per kilogram of body weight) and maximal oxygen consumptions. The oxygen cost of exercise was normal in the majority of patients, although some appeared to have abnormally high oxygen consumptions during exercise. Breathing patterns during exercise, particularly in regard to onset of hyperventilation, were similar in patients and controls.

Adolescent↗
PubMed1979

Fasting as a provocative test in neuromuscular diseases.

A 38-hr fast was used as a provocative test in patients suspected of having defects in muscle substrate utilization. In five controls and nine patients, exercise capacity and respiratory exchange ratio were determined before and at the end of the fast. Blood was collected at intervals during the fast from ten controls and nine patients for creatine kinase (CK), free fatty acids, (FFA) beta-hydroxybutyrate, acetoacetate, free and total carnitine, glucose, and alanine. Two patients with myophosphorylase deficiency had increased exercise capacity, and a marked fall in CK, and one had a lesser fall in blood glucose than normal at the end of the fast. Two patients with known lipid myopathies (carnitine deficiency and carnitine palmityl transferase deficiency) had decreased exercise capacity and apparent increased dependence on carbohydrate metabolism during the fast. Carnitine concentrations became even more abnormal in the patient with carnitine deficiency during fasting. Several patients with less well-defined defects were also significantly different from the controls in several respects, indicating that the fast might be useful for finding new defects.

Adult↗
PubMed1979

The prolonged exercise test.

The response to a standardized exercise test was investigated in 12 volunteers and 13 patients with aches, cramps, and pains. In men, creatine kinase (CK) levels peaked (up to 1600 mU per milliliter) between 10 and 20 hours after exercise. High levels of blood lactate during exercise were related to the intensity of work and to high levels of CK after exercise. The patients could be divided into several groups: (1) those with no change in blood metabolites (psychogenic); (2) those with a disproportionate rise in CK (metabolic myopathies); (3) those with a disproportionate rise of lactate (mitochondrial abnormalities); and (4) in one patient with exercise-related pains, subnormal elevation of fatty acid levels. The correlation of changes in blood lactate, CK, and fatty acids may be useful, whereas an isolated measurement, even if outside the normal range, is often meaningless.

Adult↗
PubMed1979

Increased serum creatine kinase after exercise: a sex-linked phenomenon.

The effect of 2 hours of exercise on the serum creatine kinase (CK) level was investigated in 11 men and 9 women. The mean increase of CK 24 hours after exercise was significantly greater in men. The relative lack of CK elevation in women may: (1) indicate that female muscle is less susceptible to damage by adverse factors; and (2) explain discrepancies in previous reports.

Creatine Kinase↗
PubMed1976

Muscle pathology of myotonia congenita.

We have investigated the muscle biopsies of 8 patients with myotonia congenita. There were 2 families with autosomal recessive inheritance (5 cases), 1 with autosomal dominant inheritance, and 2 sporadic cases. Mild abnormalities were seen with routine pathological preparations which were nondiagnostic. Histochemical studies of fiber subtypes demonstrated a complete absence of Type 2B muscle fibers in all of our patients regardless of the type of inheritance. this is the first reporot of an entity in which there is a consistent absence of a muscle fiber type, and some speculation has been made as to the possible causes.

Adenosine Triphosphatases↗
PubMed1976

Inflammatory myopathy, IgA deficiency, and intestinal malabsorption.

Two IgA-deficient children with inflammatory myopathy and intestinal malabsorption were evaluated. The myopathy was characterized by weakness of facial and proximal limb muscles, increased serum concentrations of lactic dehydrogenase and creatine phosphokinase, and histologic evidence of inflammation and degeneration of muscle fibers. Features of the intestinal abnormality were blunted villi, interstitial inflammation, and reduction in IgA-containing plasma cells and IgA content of epithelial cells. The myopathy and malabsorption improved with corticosteroid treatment. Circulating antibodies to striated muscle could not be demonstrated in either patient, but one had antibodies to milk and chicken serum proteins. We speculate that IgA deficiency may predispose to the development of inflammatory myopathy.

Autoantibodies↗