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Title: Biochemical studies of muscle in health and disease
Author: Smith, Ian
ISNI:       0000 0001 3439 7200
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1977
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Reconstituted commercial kits for serum enzyme assay were found to be contaminated, apparently by the very enzyme to be measured. With multiple-assay kits using kinetic methods saline instead of serum gave blank values that could be subtracted from the readings obtained to give dependable results. However, with boxes of single-assay vials the between-vial variation in contamination was substantial and, in diagnosis, could lead to unfortunate clinical consequences. Recently serum pyruvate kinase (PK) has been reported superior to creatine phosphokinase (CPK) in diagnosing Duchenne muscular dystrophy (DMD) patients and carriers. The allosteric properties of the PK isoenzyme abundant in muscle allowed both forms to assayed and compared with CPK. Normal ranges were obtained for CPK using 2 different thiol activators and for k PK modalities; both sex and seasonal differences were noted. CPK in clotted blood and serum retained its activity, on storage at room temperature and lower, far better than did PK, which lost activity when kept as serum though whole blood chilling caused its gross efflux from blood cells. CPK elevations in known DMD carriers were much more decisive than those of PK, which were frequently equivocal and only barely above the normal upper limit. CPK is accordingly markedly superior to PK in sensitivity, stability and convenience. Deducting the adenylate kinase increment (AKI) further refined the CPK assay, eliminating the effect of haemolysis in diagnosis and enabling studies of blood cell contents. Differential centrifugation separated rbcs from wbcs; and although chilling and disruption showed both had a high PK content, only the former contained an appreciable amount of CPK. The erythrocyte content of CPK appeared to match that of serum, as if by rapid passage across the cell membrane. Reasons are given to suggest that DMD may have some origin in a severe deficiency of total muscle adenine nucleotides, and thus perhaps in some defect of purine metabolism. Using double-blind techniques this possibility was tested in 16 DMD patients by giving oral allopurinol, a synthetic inhibitor of the purine catabolic enzyme xanthine oxidase, in an attempt to increase the adenine nucleotides of muscle by better salvage and recycling of available purines. Sublingual procaine adenylate was also tested. Instances of clinical improvement quickly occurred, statistically significant and accompanied by significant increases in physical strength and urinary creatinine output, together with the expected decrease in both serum and urinary urate values. At muscle biopsy ATP v/as found to be reduced to k-0% of normal in untreated patients, but after a year on daily allopurinol this more than doubled to 81% of normal, accompanied by an even larger increase in creatine phosphate (CP). As initial clinical improvements have been maintained for over a year, the view that DMD may be the expression of some defect in purine synthesis is plainly upheld. Indeed, sustained clinical arrest in this otherwise relentlessly progressive disease may even appear possible.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available