Connective tissue metabolism in normal and atrophic skeletal muscle

The pentose phosphate pathway in skeletal muscle under patho-physiological conditions. A combined histochemical and biochemical study

Over the last 30 years, research into the neuromuscular apparatus, has expanded greatly. Multidisciplinary investigations have rapidly advanced our understanding both of diseases and of the basic neuromuscular mechanisms. The mode of pathological reaction of the neuromuscular apparatus is now quite well understood. The most notable aspect of the reaction of the injured neuromuscular apparatus is the remarkably stereotyped character of the resulting pathological changes as demonstrated by a wide variety of harmful causes, producing surprisingly similar effects. The findings of our combined histochemical and biochemical investigations presented in this monograph, are in complete harmony with the stereotyped character of the pathological changes. For example, it is particularly striking that many affected muscle fibres of patients with muscular dystrophies, congenital myopathies, inflammatory myopathies, metabolic myopathies, endocrine myopathies, or with diseases of the lower motor neuron, display an enhanced activity of both oxidative enzymes of the pentose phosphate pathway. Likewise, we found that experimental animals with disordered skeletal muscles, provoked by different types of agents or treatments, reveal the same marked rise in activity of GPDH and PGDH in the muscle fibres, with a positive correlation between the activity of both enzymes. Other findings of our investigations point to a positive correlation between the activity of GPDH and PGDH on the one hand and that of the non-oxidative enzymes of the pentose phosphate pathway, the enzymes TA, TK, RPI and RPE on the other hand. The rise in activity of PGDH and, in particular, of GPDH is regulated by two different mechanisms. The first represents a rapid control mechanism based on the stimulation of both oxidative enzymes of the pentose phosphate pathway by NADP+ and on their inhibition by NADPH. The other mechanism represents a long-term effect directed at the synthesis of the enzymes. It is this type of mechanism which is responsible for the rise in activity of GPDH and PGDH we observed. The findings obtained with the applied enzyme histochemical techniques clearly demonstrated that the rise in activity of both enzymes is not homogeneously distributed in the disordered skeletal muscles of man and experimental animals. For that reason, in order to obtain reliable quantitative information about enzyme activities in the muscle fibres themselves, the application of biochemical assays on a micro-scale was indispensable. The biochemical assay of enzyme activities was performed on histologically and histochemically selected dissected muscle specimens.(ABSTRACT TRUNCATED AT 400 WORDS)

Glucose uptake and flux through phosphofructokinase in wounded rat skeletal muscle

Skeletal muscle injured with lambda-carrageenan has increased aerobic glycolysis. To assess the regulation of this process, the tissue concentrations of glycolytic intermediates, the flux through phosphofructokinase (PFK), and the intracellular concentrations of PFK effectors were examined in wounded rat skeletal muscle and in macrophages, the predominant inflammatory cell in the early stages of this wound model. Autoradiography demonstrated increased 2-deoxy-D-glucose uptake in wounded tissue compared with nonwounded muscle. 2-Deoxy-D-glucose was localized to the cellular infiltrate. The glycolytic intermediate concentrations demonstrated a facilitation of PFK in macrophages and wounded tissue as compared with nonwounded muscle. Wounded tissue had twice the flux through PFK compared with nonwounded muscle (10.0 +/- 0.6 wounded vs. 4.9 +/- 0.4 mumol.h-1.g-1 nonwounded). Macrophages had the highest flux through PFK (63.7 +/- 5.7 mumol.h-1.g-1) and when coincubated with muscle, the combined flux through PFK was equal to that of wounded muscle. The increase in glycolysis associated with wounded tissue may be explained by increased glucose uptake and increased flux through PFK by the inflammatory cells present in wounded tissue.

Additional biochemical criteria in the differential diagnosis of myositis

Thirty-six biopsy specimens of human biceps and vastus lateralis muscles were examined by histometric analysis and determination of enzyme activities (phosphorylase, triosephosphate dehydrogenase, 3-hydroxacyl-CoA-dehydrogenase, lactate dehydrogenase, hexose isomerase, citrate synthetase, 6-phosphogluconate dehydrogenase). The series included 13 specimens from patients suffering from a benign form of muscular dystrophy (limb girdle and Becker type of muscular dystrophy) and 12 specimens from patients with an acute (n = 5) or chronic (n = 7) form of myositis. Muscle fibres were atrophic in myositis and hypertrophic (with an increased variation of fibre diameters) in muscular dystrophies, as has been shown previously. When myositis samples were compared with either normal or dystrophic muscles, a highly significant lowering of glycolytic enzyme activity was found in chronic myositis, while the activity of 6-phosphogluconate dehydrogenase was elevated to highly significant levels. Measurements of the latter enzyme's activity might be of additional value in differentiating chronic forms of myositis from benign muscular dystrophies.

Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase activities in early stages of development in dystrophic chickens

Glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activities were assayed in superficial pectoral muscles of hereditary dystrophic chickens, 1 week, 2 weeks, 4 weeks and 4 months after hatching. In control chickens, activities of G6PDH and 6PGDH were very low at 4 months of age; however, at 1 week of age, they were much higher than those at 4 months of age. Activities of G6PDH and 6PGDH were significantly higher in dystrophic chickens compared with those in the controls at all the stages of development studied. These findings suggest that considerable activities of G6PDH and 6PGDH are present within the pectoral muscle cells at early stages of development, at least in dystrophic chickens. GAPDH activity was significantly lower in dystrophic chickens at 2 weeks, 4 weeks and 4 months of age compared with those in control chicken. These findings together with our previous studies (Mizuno 1984a,b) in which increased activities of superoxide dismutases, catalase, glutathione peroxidase and glutathione reductase were reported in dystrophic chickens, indicate the presence of an increased capacity for the turnover of oxygen-free radicals within muscle cells in dystrophic chickens, and that oxygen-free radicals and the related activated oxygen species may be playing a role in inducing cellular damage.

Size and strength of the quadriceps muscles of old and young women

Muscle weakness and wasting may be evaluated objectively by dynamometry and compound ultrasound imaging. We have measured the voluntary isometric strength of the quadriceps muscles of healthy women in their 70s (n = 25) and in their 20s (n = 25) and have compared it with the mid-thigh cross-sectional area of the same muscles. The two groups of women showed similar variability when strength was measured on consecutive days (coefficients of variation: 8%). The older women were 35% weaker than the young women (P less than 0.001) and their quadriceps cross-sectional area was 33% less (P less than 0.001). Quadriceps strength and cross-sectional area were correlated (r = 0.66, P less than 0.001, elderly; r = 0.53, P less than 0.01, young) and the principal axis of the relationship was closely similar for the two groups of women. There is therefore no difference in the intrinsic strength of the quadriceps muscles of healthy women in their third and eighth decades. This report also provides normative data for the objective evaluation of quadriceps weakness and/or wasting in female patients. The techniques involved are straightforward, the dynamometer is easily made, and compound ultrasound imaging is widely available.

Concepts of multiple congenital contractures (arthrogryposis) in man and animals

This is a concept of multiple congenital contractures, based upon clinical experience with the malformation and available literature, leading to a conception of the multiple categories of etiology, which cause neuropathic or myopathic muscle weakness or limb immobilization. The muscle weakness and imbalance of muscle power around the joints elicits a physiological compensatory collagenic response, which replaces atrophied muscle fibers with connective tissue and thickens the joint capsule sufficiently to result in prenatal fixation of limb segments at the joint.

Creatine kinase activity in normal and Duchenne muscular dystrophy fibroblasts

Cultured human skin fibroblasts from 9 patients with Duchenne muscular dystrophy (DMD) and 8 normal age- and sex-matched controls were examined for creatine kinase (CK) activity. Both the normal and the DMD fibroblasts were found to have significant levels of CK activity (approximately 10 x 10(-3) IU per milligram of fibroblast protein). The control cells had slightly higher CK activity than the DMD lines, but this difference was not significant (0.2 less than P less than 0.1). The MM (muscle) isozyme, the BB (brain) isozyme, and the MB (hybrid) isozyme, of CK were found to be present in fibroblasts. The isozymes were separated by electrophoresis and the relative amount of each was determined for both normal and DMD cells. In normal fibroblasts, approximately 48% of the total CK activity was of the MM type, 40% was of the BB type, and 12% was of the MB type with no significant differences apparent between normal and DMD groups. The presence in human fibroblasts of significant levels of CK activity with a characteristic isozyme profile is an important consideration for studies of this "marker" enzyme in the pseudohypertrophic muscle of DMD.