Search PubMed⌕ Search

Biomedical subjects

G A Nicholson

Publications and source records attributed to G A Nicholson.

At least 91 records · Page 5Linked to original sources
PubMed1984

A study of platelet protein phosphorylation in Duchenne muscular dystrophy. Further evidence against the generalised membrane defect theory.

As a test of the generalised defect theory for Duchenne muscular dystrophy (DMD), basal and calcium-dependent platelet protein phosphorylation was examined in order to determine if the increased concentration of calcium in DMD skeletal muscle is reflected in DMD platelets. Protein phosphorylation was quantitated by gradient slab gel electrophoresis and autoradiography. The number of phosphoproteins in each phosphoprotein peak was determined by comparison with two-dimensional gel electrophoresis. Many phosphoprotein peaks were present in unstimulated platelet preparations both in whole platelet homogenates and in intact platelets. Two of these phosphoprotein peaks were calcium-dependent, one was a single phosphoprotein, the other consisted of 4 phosphoproteins. No disease-related differences were observed in either basal or calcium-stimulated phosphoproteins. These results do not support previous reports of platelet abnormalities in DMD, and provide further evidence that the biochemical defect in Duchenne muscular dystrophy is neither generalised nor a membrane defect. The biochemical defect in DMD should be regarded as a skeletal muscle abnormality until proved otherwise.

Blood Platelets↗
PubMed1983

Acetylcholine receptor antibody in the diagnosis of myasthenia gravis.

The acetylcholine receptor (AchR) antibody assay has a key role in the diagnosis of myasthenia gravis. In this article, the role of AchR antibody assay in the diagnosis of ocular and generalized myasthenia gravis is reviewed, and compared to standard means of diagnosing the disease by clinical and electrophysiological methods.

Autoantibodies↗
PubMed1983

A sensitive assay for creatine kinase in serum samples dried on paper: enhanced thermal stability of the dried enzyme.

A new bioluminescent creatine kinase (CK) assay using purified luciferase was used to analyse CK activity in serum samples dried on filter paper. Enzyme activity was preserved for over 1 wk on paper stored at room temperature. At 60 degrees C, CK activity in liquid serum samples was rapidly inactivated, but the activity of enzyme stored on paper was preserved for at least 2 days.

Clinical Enzyme Tests↗
PubMed1983

Comparison of diagnostic tests in myasthenia gravis.

Results of 3 tests, intravenous edrophonium chloride, EMG, and acetylcholine receptor antibody testing, were compared in patients with generalised and ocular myasthenia gravis. None of the 3 tests was positive in any patient with a diagnosis other than myasthenia. However, equivocal results were obtained with edrophonium and EMG testing in some patients with myasthenia gravis and in patients with other diseases. It is concluded from this survey that antibody and edrophonium testing were equally efficient in detecting generalised myasthenia gravis. Edrophonium testing was superior in ocular myasthenia gravis. Although the yields from each test varied, all 3 tests were needed for the evaluation of some myasthenia gravis patients as each test may provide additional information.

Autoantibodies↗
PubMed1982

Decreased A23187-induced chemiluminescence in Duchenne muscular dystrophy granulocytes.

A number of recent reports suggest that intracellular calcium concentration is increased in skeletal muscle in duchenne muscular dystrophy (DMD). Leucocyte chemiluminescent responses are dependent on calcium ions and can be induced by the calcium ionophore A23187. Chemiluminescence may therefore reflect intracellular calcium levels. In order to determine whether non-muscle cells in DMD share the calcium abnormality, we have examined A23187-induced chemiluminescence in DMD leucocytes. Peak calcium dependent chemiluminescence occurred at 0.25-0.75 mM added calcium chloride. Peak chemiluminescent responses in the 13-paired samples were reduced in DMD leucocytes (P less than 0.01) using a paired t-test. These result suggest that there is an abnormality of calcium dependent A23187-induced chemiluminescence in DMD leucocytes and that there may be a generalised abnormality of calcium metabolism in DMD.

Anti-Bacterial Agents↗
PubMed1982

An evaluation of lymphocyte capping in Duchenne muscular dystrophy.

There have been conflicting reports of lymphocyte capping abnormalities in Duchenne muscular dystrophy (DMD). We have evaluated the original method described by Verrill et al. in a "blind" study of 24 Duchenne muscular dystrophy boys and paired age-matched control boys. We found no differences in capping between the two groups but control boys had decreased capping compared to a group of normal adult males and females. It is concluded that the initial reports of decreased capping in DMD may have been due to differences in age between the test and control group.

Adult↗
PubMed1981

Plasma creatine kinase isoenzymes in the Bar harbor dystrophic mouse.

Increased activity of the MM isoenzyme of creatine kinase (CK) was found in plasma from Bar Harbor dystrophic mice of the 129/ReJ dy/dy strain when compared to the findings in non-dystrophic controls. Total plasma CK activity was only slightly increased in dystrophic animals but plasma from both normal and dystrophic mice showed large amounts of the BB isoenzyme of creatine kinase. This isoenzyme was also found to be present in mouse platelets. It is concluded that BB isoenzyme from platelets could have obscured the contribution of muscle CK to the total plasma CK activity and the CK isoenzyme quantitation is needed to evaluate muscle disorders in rodents.

Animals↗
PubMed1981

Carrier testing in families of isolated cases of duchenne muscular dystrophy. Creatine kinase activities in female relatives of mothers with normal CK activity.

A study of the serum creatine kinase (CK) activity in the female relatives of mothers of isolated cases of Duchenne muscular dystrophy (DMD) was undertaken.. It was restricted to the relatives of mothers with normal serum CK values. Ninety-eight females in 19 families were studied; none was found to have a serum CK activity more than 3 SD above the normal mean. This evidence, derived from a study in which the measurement of serum CK activity was used as the sole means of detecting carriers, suggests that very few distant female relatives in such families are carriers of the gene and provides some evidence against the hypothesis that mutation is a rare cause of isolated cases of Duchenne muscular dystrophy.

Adolescent↗
PubMed1981

Acetylcholine receptor antibodies in the diagnosis and management of myasthenia gravis.

The relationship of acetylcholine receptor (AchR) antibodies to disease activity in myasthenia gravis (MG) is controversial. Some authors claim a direct correlation with disease activity and treatment, in particular plasmapheresis therapy, whereas others have commented on the poor overall correlation of antibody levels with clinical state. Antibody levels were examined in a population of MG patients and correlated with disease activity and response to treatment. Antibodies to skeletal muscle AchR were found in most patients with generalised MG (24/25) and in about half of the patients with purely ocular MG (6/10) and in neither of 2 patients with congenital MG. There was scant correlation with disease activity or response to treatment. It is concluded that the assay is more useful for diagnosis than for management of MG.

Antibodies↗
PubMed1979

Carrier detection in Duchenne muscular dystrophy: Assessment of the effect of age on detection-rate with serum-creatine-kinase-activity.

In 40 known carriers of the gene for Duchenne muscular dystrophy (mean age 38 years) the detection-rate with a standard assay of serum-creatine-kinase was 53%. In 52 daughters of known carriers (mean age 16 years) the detection-rate was 45% after correction of age. This implies a much higher detection-rate (about 90%) in young carriers and suggests that discrimination between carriers and noncarriers may best be achieved by testing in childhood.

Adolescent↗
PubMed1979

An evaluation of some carrier detection techniques in Duchenne muscular dystrophy.

Some recently described abnormalities in the serum and red cell membranes in Duchenne dystrophy have been examined as methods of carrier detection in a single-blind controlled study. Twelve carriers (4 definite, 3 probable and 5 possible carriers previously found to have raised creatine kinase levels) and 12 normal female controls of the same age, were examined on 3 separate occasions at approximately two-weekly intervals. Analysis of age-dependent red cell shape changes, serum haemopexin levels, red cell K+ efflux rate, sensitivity of red cell ghost membrane ATPase to ouabain, membrane protein phosphorylation studies and lactate dehydrogenase isoenzyme profiles on agarose gel electrohoresis all failed to distinquish carriers from controls. The carriers suffered muscle cramps more frequently than the controls and all but one carrier and two control subjects were correctly identified by manual muscle strength testing, certain proximal muscles in paricular being consistently weaker in carriers than in the control group subjects. Scalar electrocardiography revealed higher values for the R/S ratio in Leads V1 and V2 and the sum (R-S) in V2.

Adenosine Triphosphatases↗
PubMed1978

Radioimmunoassay of creatine kinase: studies on the skeletal muscle and cardiac muscle enzyme (MM and MB isoenzymes) in serum and neuromuscular tissues.

A radioimmunoassay, specific for the isoenzymes of creatine kinase containing the M subunit of the enzyme (MM and MB creatine kinase), was employed to determine total creatine kinase concentrations in serum and neuromuscular tissues independently of the state of activity of the enzyme. This technique provides a method for the detection of inactive enzyme, which could be produced by inhibitors of the enzyme or by mutations involving the active site of the enzyme. A series of experiments were carried out to compare the amount of creatine kinase in various samples as assessed by normal enzyme kinetic procedures and by radioimmunoassay. The two techniques yielded equivalent results in all situations tested. Samples included serum from normal subjects and subjects with genetic and acquired diseases of muscle and also extracts from skeletal and cardiac muscle. Small quantities of immunoreactive enzyme were found in nervous tissue and assessed in terms of the incidence of the M subunit.

Abdominal Muscles↗