The increase in activity of acid hydrolases in muscles of rats after subcutaneous administration of dimethyl-para-phenylene diamine. A combined histochemical and biochemical investigation. I. The histochemical investigation

Criteria for the validation of quantitative histochemical enzyme techniques

Some practical criteria are suggested for establishing the precision, reproducibility, validity and specificity of quantitative histochemical techniques used for assaying the activities of enzymes in single cells and tissue sections. To be valid, a technique should ideally pass 12 tests. Principally these involve proving that the mean absorbance or fluorescence of the specific final reaction product (FRP) is related to section thickness, incubation time, substrate concentration and the concentration of enzyme in situ. However, the formation of appreciable amounts of non-specific FRP may interfere in the determination of the true enzyme activity. This and other difficulties are illustrated with data obtained from an investigation of Meijer's semipermeable membrane technique for assaying acid phosphatase in unfixed sections of muscle.

Semipermeable membrane techniques in quantitative enzyme histochemistry

Non-structurally bound, partially structurally bound or weakly structurally bound enzymes diffuse out of sections during the histochemical incubation period. Fixation of sections does not help to prevent diffusion since the enzymes may be inactivated by their chemical reaction with the fixative. Moreover watery fixatives cause partial leakage of enzymes into the fixative solution. The inclusion of macromolecular substances in the incubation media only partially prevents the leakage of enzymes. In the technique discussed here a semipermeable membrane is interposed between the incubating solution and the tissue section. Because only molecules with a molecular weight of 20 000 can penetrate the membranes, diffusion of enzymes is prevented, whereas substrate molecules and other components necessary for the staining reaction diffuse through the membrane. This technique is suitable for the histochemical demonstration of activity of oxidoreductases, transferases, hydrolases and isomerases. Particular attention is paid to how far semipermeable membrane methods are suitable for quantitative histochemical studies of enzymes.

Lysosomal changes in mouse skeletal muscle during the repair of exercise injuries

Lysosomal changes of mouse skeletal muscle during the repair of exercise injuries were studied with biochemical, histochemical, and electron microscopic methods. Treadmill running for 4 hours and 9 hours increased the activities of cathepsin C and beta-glucuronidase, but not that of beta-glycerophosphatase in mouse quadriceps femoris muscle. The highest activities occurred 3 days after exertion and were higher after the longer duration of exertion. Similar changes that were highly correlated with the activities of lysosomal enzymes occurred in the activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and in the concentration of DNA. The activities of lysosomal enzymes correlated significantly with the severity of histopathologic injuries. Histochemical stainings of beta-N-acetylglucosaminidase and beta-glucuronidase showed a strong increase in the staining intensity 3 and 5 days after exertion, both in inflammatory phagocytes and in surviving muscle fibers in the injured area, and staining intensities increased in parallel with the severity of injuries. Electron microscopy showed an increased number of autophagic vacuoles, lysosome-like bodies, and Golgi complexes in the fibers adjacent to necrotic foci, coinciding with the highest histochemical staining pattern. Lysosomal changes in surviving muscle fibers in close proximity to injured muscle fibers could, by autophagic degradation, provide structural elements for the regeneration of injured muscle fibers.

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)

Enzyme histochemistry on muscle biopsies as an aid in the diagnosis of diseases of the equine neuromuscular system: a study of six cases

Muscle biopsies from six horses with clinical histories of muscle atrophy, muscle tremors, myopathic symptoms, unsteadiness of pelvic limbs and progressive ataxia were examined. Muscle biopsies were studied with enzyme histochemical techniques to evaluate the diagnostic values of these methods in cases suspected of suffering from neuromuscular disorders. Hypertrophy, atrophy, fibre splitting, waxy degeneration, phagocytosis and necrosis were seen in haematoxylin eosin stained sections of the different cases. Fibre type predominance and fibre type grouping were seen in the calcium ion stimulated myosine ATP-ase (Ca-ATP-ase) stained sections of some cases. 'Moth-eaten fibres' were demonstrated in three cases by staining with NADH: nitro blue tetrazolium oxidoreductase (NADH-TR), succinate dehydrogenase (SDH), NADH dependent malate dehydrogenase, cytochrome c oxidase and by lactate dehydrogenase. The catabolic enzymes, acid phosphatase (ACP) and 5'-nucleotidase were active in cases with fibre phagocytosis. The oxidative part of the pentose phosphate pathway in myopathic tissue seemed to be important in three cases, demonstrated by the increased activity of glucose-6-phosphate dehydrogenase (GPDH) and 6-phosphogluconate dehydrogenase (PGDH). The important feature of diseased horse muscle was that the pathohistochemical changes were exactly the same as in diseased skeletal muscles of humans. The application of tissue saving enzyme histochemical techniques can be recommended in the study of muscle tissue from horses suffering from suspected neuromuscular disorders.

The inhibitory effect of actinomycin D and cycloheximide on the increase in activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in experimentally induced diseased skeletal muscles

The myotoxic effect of the subcutaneous administration of N,N1-dimethyl-p-phenylenediamine (DPPD) in rats was enhanced by the simultaneous administration of hyaluronidase. The resulting myopathy was associated with an early and dramatic increase in activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Administration of actinomycin D or cycloheximide prior to the combined DPPD and hyaluronidase treatment prevented the increase in activity of both pentose phosphate pathway enzymes, indicating that the increase in activity requires RNA synthesis and protein synthesis. The possibility that the increase in activity of both NADPH-regenerating enzymes results from the modification by effectors of existing less active forms of these enzymes leading to more highly active forms was refuted.

Lysosomal changes related to exercise injuries and training-induced protection in mouse skeletal muscle

Three experiments were designed to study the lysosomal changes associated with the development and maintenance of the endurance training induced resistance against exercise injuries in mouse skeletal muscles. The activities of arylsulphatase, cathepsin C, cathepsin D, and beta-glucuronidase were assayed from the red part of mouse quadriceps femoris muscle 4 days after prolonged strenuous running of 4-9 h duration. Exercise injuries were characterized by necrotic fibers and focal inflammation. Strenuous running of untrained mice induced necrotic lesions and a 4-5 fold increase in the activities of lysosomal enzymes. This lysosomal response was considerably reduced already by daily training bouts on the 3 days preceding the strenuous exertion. Simultaneously exercise injuries were markedly reduced. Extending the endurance training program increased the running ability of mice and further reduced the necrotic lesions and lysosomal changes induced by the strenuous exercise. The detraining of 1 week after the termination of regular endurance training considerably increased the degree of exercise induced lysosomal response. The detraining of longer durations further increased the lysosomal response and no effect of prior endurance training existed after 1 month detraining. Our observations suggest that the severity of exercise injuries is related to the strength of the exercise stimulus and the level of preceding physical activity and can be characterized by the lysosomal changes.

Autophagic response to strenuous exercise in mouse skeletal muscle fibers

Strenuous physical exercise induces necrosis of skeletal muscle fibers and increases lysosomal enzyme activities in surviving muscle fibers. This study examines the ultrastructural basis of the stimulation of the lysosomal system in mouse vastus medialis muscle during the appearance and repair of exercise-induced (9 h of running) injuries. Necrotic fibers appeared the day after exercise and an inflammatory response with the replacement of necrotic fibers by phagocytes was highest 2-3 days after exertion. Ultrastructural study of surviving muscle fibers revealed numerous autophagic vacuoles, residual bodies, and spheromembranous structures at the periphery of myofibers, especially in fibers adjacent to necrotic fibers. The autophagic response was most prominent between 2 and 7 days after exertion. Autophagic vacuoles with double or single limiting membranes contained mitochondria at various stages of degradation. Vacuolar and multilamellar structures were also observed in regenerating muscle fibers. The structure of injured skeletal muscle fibers returned to normal within 2 weeks. It is proposed that increased autophagic activity could be related to the breakdown of cellular constituents of surviving muscle fibers to provide structural elements for regenerating muscle fibers.

Susceptibility of mouse skeletal muscles to exercise injuries

The susceptibility to exercise-induced myopathy was studied by histological and biochemical methods in various skeletal muscles of mice 3-4 days after a single bout of prolonged running. The degree of exercise injuries varied greatly in different muscles. Soleus and the red deep parts of quadriceps femoris were the most severely affected muscles. Extensive or scattered necrosis of muscle fibers was associated with focal inflammation and a five- to nine-fold increase in the activity of beta-glucuronidase in these muscles. Slight necrotic changes and a two- to three-fold increase in the activity of beta-glucuronidase were observed in tibialis anterior, plantaris, and the red deep parts of gastrocnemius. A statistically significant increase in beta-glucuronidase activity was also observed in the white distal part of quadriceps femoris, biceps femoris, gracilis, extensor digitorum longus, and peroneal muscles but necrotic lesions were infrequent in these muscles. The degree of exercise injuries is probably affected by the different recruitment of muscles during running and by the anatomical location of muscles in separate compartments, which could expose them to different levels of ischemic compression by postexercise edema.

Lipid peroxidation in exercise myopathy

Selected estimates of lipid peroxidation were analyzed in mouse quadriceps femoris muscle immediately after submaximal prolonged (9 hr) and exhaustive maximal running (2-3 hr), and at intervals 1-10 days afterward during the exercise-induced myopathy. Immediately after the two types of exertion no significant changes were observed in the concentrations of lipid peroxidation products (thiobarbituric acid (TBA) reactive substances, and lipofuscin) or in the estimates of autoxidation (spontaneous and Fe2+-induced autoxidations) and antioxidant (catalase, glutathione peroxidase, and vitamin E) capacities. The enzymatic estimate of exercise myopathy (beta-glucuronidase) increased considerably (2-6 days) after both types of exertion. Simultaneously, the lipid peroxidation rate of muscle homogenates in vitro increased markedly and in highly significant correlation with the activity of beta-glucuronidase. The concentrations of TBA reactants and lipofuscin as well as Fe2+-induced lipid peroxidation were not affected during exercise myopathy. The activities of catalase and glutathione peroxidase increased significantly after both exertions, while the concentration of vitamin E was unchanged. Exhaustive running of endurance-trained mice caused only slight signs of myopathy and no increase in the rate of lipid peroxidation in vitro.

Exercise myopathy: selectively enhanced proteolytic capacity in rat skeletal muscle after prolonged running

The proteolytic capacity of rat skeletal muscle was analyzed during the repair of fiber injuries after strenuous exercise. A single bout of prolonged exercise (8 hr running at a speed of 17 m X min-1) caused a slight fiber necrosis and a selective response in the proteolytic activity of rat skeletal muscle. Acid proteolytic capacity (cathepsin D and acid autolysis) was considerably increased on the 4th day after exertion and partially decreased by the 10th day. The acid hydrolytic response was more prominent in red than in white skeletal muscle. Alkaline proteolytic capacity (alkaline and myofibrillar proteases), increased in several atrophic myopathies, was not affected in exercise myopathy. The rate of neutral autolysis slightly increased after exertion. The protein content of skeletal muscle was decreased on the 4th day after exertion. We suggest that the proteolytic responses to acute injuries, as well as to chronic atrophies, are highly selective in skeletal muscle fibers.

Systemic effects of N,N-dimethyl-paraphenylenediamine hydrochloride on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat

N, N-dimethyl-paraphenylenediamine (DMPPD) hydrochloride increases the inorganic and organic acid-soluble phosphate (Pi and POAS) uptakes in the innervated gastrocnemius muscle of the rat but not in the innervated soleus. In the denervated gastrocnemius muscle, the effects of DMPPD and denervation are not additive, Pi uptake being even lower than on the controlateral innervated side. It is suggested that DMPPD acts only on the innervated fast fibre (white fibre, type II anaerobic fibre), as far as the permeability to Pi is concerned. Histological evidence of a severe myopathic process affecting slow and fast fibres, irrespective of denervation has been documented. Severe degenerative changes were still manifest after a 20-day DMPPD treatment. There is no obvious relation between the biochemical alterations in phosphate metabolism and the morphological lesions. The increased Pi and POAS uptakes observed in the innervated gastrocnemius and soleus muscles during generalized convulsions induced by DMPPD are independent of a direct drug action on the muscle fibre.

The increase in activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in skeletal muscles of rats after subcutaneous administration of N,N'-dimethyl-para-phenylenediamine

After subcutaneous administration of N,N'-dimethyl-para-phenylenediamine (DPPD) in rats, a myogenic myopathy was produced in the skeletal muscles. In this communication, the results of the application of various histochemical techniques for the localization of oxidoreductases, transferases, hydrolases and isomerases and biochemical techniques for the estimation of activities of oxidoreductases in the experimental skeletal muscles are presented. The most striking results was the activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase which increased dramatically during the early phase of the muscle disease. The increase in activity of the pentose phosphate shunt enzymes was the first pathological alteration and was present as early as 8 h after a single injection of DPPD. Histochemical techniques for demonstration of activity of both enzymes are therefore highly suited for the detection of minor diseases and the early onset of major diseases of the neuromuscular system. Some glycolytic enzymes as well as some enzymes of the aerobic part of the metabolism showed an early decrease or increase in activity indicating a metabolic imbalance in the muscle fibres. There were more fibres with an intermediate pattern of the energy yielding enzymes in the experimental muscle specimens then in specimens from the control groups. The activity of the catabolic hydrolytic enzymes was strongly increased in pathological muscles. The aerobic muscles were more vulnerable to DPPD than the anaerobic muscles.