Improved detection of Duchenne muscular dystrophy heterozygotes using discriminant analysis of creatine kinase levels

Echinogenic action of L-alpha-lysophosphatidylcholine in Duchenne muscular dystrophy: a study on carrier detection

The percentage of echinocytes induced after red cell treatment with L-alpha-lysophosphatidylcholine in the blood of 16 patients affected by Duchenne muscular dystropy (DMD) has been evaluated. Moreover, 15 mothers, 10 sisters, and 15 fathers were also included in the study. We found an increased level of echinocytes in dystrophic patients and in known and possible carriers. Correlations were also evaluated between echinocytes and serum enzymes used in DMD diagnosis, showing an increase of echinocytes also in DMD carriers with normal levels of serum creatine kinase, lactate dehydrogenase, and aldolase. Our results suggest that the sensitivity of erythrocytes to L-alpha-lysophosphatidylcholine in DMD could be used as a diagnostic test for carrier detection.

4-Nitrophenylalkaline phosphatase inhibition in muscular dystrophy

The allosteric behaviour of 4-nitrophenylphosphatase from membrane erythrocytes was investigated in Duchenne muscular dystrophy (DMD) patients, in female carriers and in healthy controls. Cooperative type kinetics with a Hill coefficient of -2.19, -1.71 and -1.54 has been obtained from the inhibition by fluoride in controls, female carriers and Duchenne patients, respectively. Our observation supports the previously described membrane abnormalities in DMD erythrocytes and may extend then to female carriers.

Serum creatine kinase activity following forearm flexion isometric exercise

The purpose of this study was to compare serum creatine kinase (CK) activity following two forearm flexion isometric exercise regimens differing in work to rest ratio, and examine the CK response to a repeated bout of isometric exercise. Eleven males were tested on two sessions (bouts) spaced 1 week apart. For bout 1, five subjects (group A) performed a forearm flexion isometric exercise consisting of 40 10-s maximal contractions with 20-s inter-trial rests (10:20), while six (group B) performed 40 maximal 10-s contractions with 5-s inter-trial rests (10:5). The increase in serum CK activity following the 10:20 exercise (143%) was significantly greater than that following the 10:5 exercise (52%). The 10:20 exercise was also associated with greater tension generation over trials. One week later, both groups performed a bout of 10:20 exercise. A substantial reduction in the serum CK response was found following this second bout. The data suggest that for bout 1 the isometric exercise associated with the greater overall tension levels resulted in the greater CK response. However, when the 10:20 exercise was repeated 1 week later, a substantial reduction in the CK response was found which was unrelated to the tension generated.

A spin label study of the erythrocyte membrane in mothers and sisters of patients suffering from Duchenne Muscular Dystrophy

The erythrocyte membranes of mothers and sisters of boys suffering from Duchenne Muscular Dystrophy (DMD) have been studied by spin labelling. Two oxazolidine nitroxide derivatives of stearic acid were used. With the first of them (16 NS) which probes the hydrophobic part of the phospholipids, we measured the fluidity of the membrane as a function of temperature. The second nitroxide derivative (5 NS) probes the membrane near the phospholipid polar heads. The amplitude of the electron spin resonance signal was studied as a function of the spectrometer microwave power in order to determine the paramagnetic label saturation behaviour. No significant difference was observed between the control adult women and the carrier mothers. On the contrary, almost all the normal young premenarchial girls showed simultaneously a break in the fluidity vs. temperature plot of the 16 NS probe and a saturation phenomenon of the 5 NS label signal. In about 50% of the DMD boys' sisters, no break in the temperature plot nor saturation behaviour was observed. This corresponds to the theoretical repartition between normal and carrier girls if one admits that about 30% of the latter do not have any detectable membrane abnormality, as in the case of the creatine kinase (CK) test which shows about 30% of normal levels in carrier women. The study of the erythrocyte membrane in young girls can then be an useful complementary tool to detect DMD carriers.