Myopathy-dependent changes in activity of ATPase, SDH and GPDH and NOS expression in the different fibre types of hamster muscles

Changes in metabolic profile and population of skeletal muscle fibers of mice overexpressing calsequestrin: influence of losartan

In heart failure, exertional fatigue of skeletal muscles can occur. A transgenic mouse overexpressing calsequestrin can be regarded as an animal model of heart failure. The aims of the present study were to investigate, whether at the time of cardiac failure the composition of fiber types of skeletal muscles was altered, what kind of alterations in glycolytic and oxidative enzyme activities occurred in different muscle fiber types and whether these were affected by the administration of the angiotensin II receptor blocker, losartan. Hemodynamic parameters were determined using a working heart preparation. Four groups of mice were investigated: wild-type (WT) mice and transgenic (TG) mice overexpressing calsequestrin, with and without losartan treatment. Enzyme activities were measured in homogenates of Rectus femoris muscle and in muscle fibers, which were typed by their metabolic profile. Calcineurin expression was measured by Western blotting. Succinate dehydrogenase activity was increased by 275% in R. femoris muscle homogenates of TG compared to WT mice. This was due to a 57% increase in slow oxidative fibers, which was accompanied by an increased calcineurin expression in TG muscles. This increase was attenuated by losartan treatment. With respect to glycerol-3-phosphate-dehydrogenase (GPDH), no difference was evident comparing WT and TG. Treatment with losartan resulted in a down-regulation of GPDH in WT and TG. In conclusion, changes in skeletal muscles occur in this mouse model of heart failure and these changes were antagonized by losartan. In contrast to heart failure patients, in the mouse model a shift to the oxidative phenotype of skeletal muscle was noted, possibly due to enhanced calcineurin expression.

Fibre type related changes in the metabolic profile and fibre diameter of human vastus medialis muscle after anterior cruciate ligament rupture

Vastus medialis muscles of patients with chronic anterior instability of the knee after anterior cruciate ligament rupture were analysed to investigate changes in defined muscle fibres of the diseased leg in comparison to the healthy leg of the same patient. Metabolic and morphological parameters were obtained by cytophotometrical measurements of the activities of succinate dehydrogenase (a marker of oxidative metabolism) and glycerol-3-phosphate dehydrogenase (a marker of glycolytic metabolism) of slow-oxidative (SO), fast-oxidative glycolytic (FOG) and fast-glycolytic (FG) fibre types in serial sections and by measuring the minimal fibre diameters of type I (slow) and type II (fast) fibres. We found decreased glycolytic activity and a shift to more oxidative metabolism in each fibre type suggesting diminished fast force and shift to endurance force development. The latter was interpreted as a sign of active compensation for the knee instability. Significantly decreased minimal fibre diameters to 85.9% in type I fibres, and to 88.7% in type II fibres of the diseased muscle were measured, indicating the fibre atrophy. Our findings suggest that the atrophied muscle fibres of the affected vastus medialis muscle adapt to the altered conditions by changing their metabolic profile. Muscle fibres of different types were found to be affected similarly.

Compartmentalization of NO signaling cascade in skeletal muscles

Skeletal muscle functions regulated by NO are now firmly established. However, the literature on the compartmentalization of NO signaling in myocytes is highly controversial. To address this issue, we examined localization of enzymes engaged in L-arginine-NO-cGMP signaling in the rat quadriceps muscle. Employing immunocytochemical labeling complemented with tyramide signal amplification and electron microscopy, we found NO synthase expressed not only in the sarcolemma, but also along contractile fibers, in the sarcoplasmic reticulum and mitochondria. The expression pattern of NO synthase in myocytes showed striking parallels with the enzymes engaged in L-arginine-NO-cGMP signaling (arginase, phosphodiesterase, and soluble guanylyl cyclase). Our findings are indicative of an autocrine fashion of NO signaling in skeletal muscles at both cellular and subcellular levels, and challenge the notion that the NO generation is restricted to the sarcolemma.

Cellular control of nitric oxide synthase expression and activity in rat cardiomyocytes

Potential ortho- and pathophysiological roles for nitric oxide synthases (NOS) in cardiac functions have been and are continuing to be described. However, cellular signaling mechanisms controlling nitric oxide (NO) production in the heart remain obscure. The aim of this study was to investigate signaling mechanisms involved in regulation of NOS expression and NO generation in cardiomyocytes. Using immunocytochemical methods in conjunction with western blotting, we have found that cultured neonatal rat cardiomyocytes express constitutively all three NOS isoforms targeted predominantly to the particulate component of cardiomyocytes - mitochondria and along contractile fibers, as well as along plasma membrane including T-tubules. Biochemical assay of NO generation has shown that exposure of cultured neonatal rat cardiac cells to isoproterenol (beta-adrenergic stimulation), iloprost [stable prostaglandin I(2) (PGI(2)) analogue], as well as inflammatory cytokines and dibutyryl adenosine-3',5'-monophosphate (db-cAMP), resulted in a marked up-regulation of NOS expression by cardiomyocytes. In db-cAMP-stimulated cells, inhibition of protein kinase A (PKA) and protein kinase C (PKC) reduced immunolabeling of NOS and concomitantly lowered NO production. Taken together, these data point to an involvement of beta-adrenergic mechanisms, cytokine and PGI(2) receptors, adenylyl cyclase, PKA, and PKC in the control of NO generation and expression of NOS in rat cardiomyocytes.

Experimental study of effect of Ganyanping on fibrosis in rat livers

AIM: To observe the effects of Ganyanping on CCl₄-induced hepatic fibrosis in rats.

METHODS: The rats were separated randomly into five groups. Groups A to group D, each consisting of 15 rats, were for different tests, while 8 rats were used as normal controls (N). For group D, CCl₄ was injected subcutaneously, at a dosage of 3 mL/kg for 9 wk. For group A, Ganyanping was administered via gastric tube at a dosage of 10 mL/kg. For group B, the treatment with Ganyanping was started 4 wk after CCl₄ administration. In group C, Ganyanping was administered 8 wk after the intoxication, and treatment lasted for 4 wk. Liver tissues were fixed in 10% formalin and embedded in paraffin. Pathologic changes, particularly fibrosis, were evaluated on the HE and V-G-stained sections. Ten middle-power fields were randomly selected for assessment of collagen deposition.

RESULTS: Loss of normal hepatic architecture, some with pseudo-lobule formation, was observed in group D, while hepatocytes steatosis and fibrosis were less pronounced in the animals treated with Ganyanping. Pseudo-lobule formation was not evident in the latter groups. The total collagen area and ratio were 840.23 ± 81.65 and 7.0 ± 0.9, respectively in group D, the ratio being reduced greatly in the Ganyanping-treated groups (148.73 ± 45.89 and 1.16 ± 0.33, respectively). The activities of MAO and ACP were elevated and that of SDH in group D decreased in the hepatic tissue as compared to the control group. The treatment with Ganyanping abrogated these enzymatic changes.

CONCLUSION: Our data approved that Ganyanping could improve the microcirculation in the liver, reduce oxygen-derived free radicals, and enhance the cellular metabolism and immune function, all resulting in an anti-fibrotic effect. Hence, Ganyanping can protect the liver from fibrosis. It may be a safe and effective preparation for patient with fibrosis.

Cytophotometrical and immunohistochemical analysis of soft palate muscles of children with isolated cleft palate and combined cleft lip and palate

Palatal muscle biopsies from the cleft margin of children were subjected to cytophotometrical and immunohistochemical analysis. Muscle fiber types were classified according to the enzyme activity of myofibrillic adenosine triphosphatase, glycerol-3-phosphate-dehydrogenase and succinate dehydrogenase assessed cytophotometrically. Fiber type-related immunoreactivity of nitric oxide synthase (NOS) isoforms I, II, III, as a physiological modulator of skeletal muscle function, was related to the oxidative and glycolytic activity of the muscle fibers. Fast oxidative glycolytic fibers with high oxidative activity showed strong NOS I immunoreactivity, whereas fast glycolytic fibers with high glycolytic activity were stronger immunolabelled for NOS III. NOS II expression was similar in all fiber types. No differences in NOS immunoreactivity were found between the two investigated forms of deformity. Additionally to the usual skeletal muscle fiber types, a slow tonic fiber type was for the first time identified in cleft palate muscles. Comparison of two forms of cleft palate, isolated cleft palate and combined cleft lip and palate has shown decreased enzyme activities in muscle fibers of palatal muscles from combined cleft lip and palate. Fast oxidative glycolytic fibers were mainly effected. Cytophotometrical and immunohistochemical analysis indicated a depressed performance of the cleft palatal muscles from combined cleft lip and palate as a stronger deformity compared with isolated cleft palate.