Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.99.1 (NADPH-diaphorase)
 3,903 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NADPH diaphorase histochemistry and NOS-1 immunohistochemistry on 60 microm thick frozen sections of rat extensor digitorum longus muscles led to the detection of prominent rings clearly encompassing the surface of the muscle fibres. These so far unknown costameres were usually found as doublets flanking a space of about 2 microm width. Because these costameric doublets did not appear in regular periods, we designate them irregular costameres to discriminate them from regular ones with a 1 microm periodicity overlying Z-discs and M-lines. Irregular costameres were thicker than the regular ones and free of intercostameres. Immunohistochemistry demonstrated that NOS-1 was co-localized with integral (beta-dystroglycan, alpha-sarcoglycan) and peripheral (caveolin-3, dystrophin) members of the enlarged dystrophin complex in the irregular costameres but not with non-sarcolemmal organized proteins (myosin heavy chain, alpha-actinin, desmin and sarcoplasmic reticulum-located Ca2+-dependent ATPase-1). Invaginations of the sarcolemma to form irregular costameres were observed. In teased myofibres the sarcolemma between two following irregular costameres was ballooned, while the irregular costameres themselves clamped the fibres together. Finally, the number of detectable irregular costameres was significantly increased in maximally contracted extensor digitorum longus muscles generated by electric stimulation but decreased in mechanically stretched ones. Combining these observations, we hypothesize that irregular costameres belong to a reserve zone for the sarcolemma necessary for the contraction/relaxation cycle in myofibres.
 ...
PMID:Irregular costameres represent nitric oxide synthase-1-positive sarcolemma invaginations enriched in contracted skeletal muscle fibres. 1125 90

Nitric oxide synthase-1 (NOS-1) is found in high concentrations in skeletal muscles, where its synthesis product nitric oxide (NO) is reported to be involved in a number of processes, including the modulation of the oxidative metabolism of myofibers. Performing immunoblot analysis and quantification of formazan produced by its specific NADPH diaphorase activity, we found NOS-1 to be enriched in rat skeletal muscles with a high proportion of fast-twitch myofibers. Since these myofibers represent a metabolically heterogeneous subpopulation, we extended our investigation to the level of individual myofibers. Using serial sections we combined myosin heavy chain-based fiber-typing with quantitative succinate dehydrogenase histochemistry to determine three groups of fiber-types, comprising fast-oxidative, fast-glycolytic and slow-oxidative myofibers. Image analysis showed that NOS-1 diaphorase activity is significantly enriched in fast-oxidative myofibers compared with fast-glycolytic and slow-oxidative ones. In order to characterize potential biological effects of the fiber-type-specific enrichment of NOS-1, we performed cytochrome oxidase histochemistry in the presence of the NO donors NOC-9 and SNAP. Both NO donors reduced cytochrome oxidase activity in all myofibers investigated with almost identical semi-maximal inhibition rates, although fast-oxidative and slow-oxidative myofibers contained twice as much basal catalytic activity than fast-glycolytic ones. In summary, we suggest that the NOS-1/NO system of skeletal muscles exerts its biological role especially in fast-oxidative myofibers, since these myofibers express more NOS-1 than fast-glycolytic or slow-oxidative ones and also contain the highest concentrations of cytochrome oxidases as potential target molecules of NO.
 ...
PMID:Nitric oxide synthase-1 is enriched in fast-twitch oxidative myofibers. 1170 44

A description is provided of the ratio of slow-tonic vs. slow- and fast-twitch fibers for five muscles in the adult turtle, Pseudemys (Trachemys) scripta elegans. The cross-sectional area of each fiber type and an estimation of the relative (weighted) cross-sectional area occupied by the different fiber types are also provided. Two hindlimb muscles (flexor digitorum longus, FDL; external gastrocnemius, EG) were selected on the basis of their suitability for future motor-unit studies. Three neck muscles (the fourth head of testo-cervicis, TeC4; the fourth head of retrahens capitus collique, RCCQ4; transversalis cervicis, TrC) were chosen for their progressively decreasing oxidative capacity. Serial sections were stained for myosin adenosine triphosphatase (ATPase), NADH-diaphorase, and alpha-glycerophosphate dehydrogenase (alpha-GPDH). Conventional fiber-type classification was then performed using indirect markers for contraction speed and oxidative (aerobic) vs. glycolytic (anaerobic) metabolism: i.e., slow oxidative (SO, including slow-twitch and possibly slow-tonic fibers), fast-twitch, oxidative-glycolytic (FOG), and fast-twitch glycolytic (Fg) fibers. Slow-tonic fibers in the SO class were then revealed by directing the monoclonal antibody, ALD-58 (raised against the slow-tonic fiber myosin heavy chain of chicken anterior latissimus dorsi), to additional muscle cross sections. All five of the tested muscles contained the four fiber types, with the ATPase-stained fibers including both slow-tonic and slow-twitch fibers. The extreme distributions of SO fibers were in the predominately glycolytic TrC vs. the predominately oxidative TeC4 muscle (TrC-SO, 9%; FOG, 20%; Fg, 71% vs. TeC4-SO, 58%: FOG, 16%; Fg, 25%). Across the five muscles, the relative prevalence of slow-tonic fibers (4-47%) paralleled that of the SO fibers (9-58%). TeC4 had the highest prevalence of slow-tonic fibers (47%). The test muscles exhibited varying degrees of regional concentration of each fiber type, with the distribution of slow-tonic fibers paralleling that of the SO fibers. In the five test muscles, fiber cross-sectional area was usually ranked Fg > FOG > SO, and slow-twitch always > slow-tonic. In terms of weighted cross-sectional area, which provides a coarse-grain measure of each fiber type's potential contribution to whole muscle force, all five muscles exhibited a higher Fg and lower SO contribution to cross-sectional area than suggested by their corresponding fiber-type prevalence. This was also the case for the slow-twitch vs. slow-tonic fibers. We conclude that slow-tonic fibers are widespread in turtle muscle. The weighted cross-sectional area evidence suggested, however, that their contribution to force generation is minor except in highly oxidative muscles, with a special functional role, like TeC4. There is discussion of: 1) the relationship between the present results and previous work on homologous neck and hindlimb muscles in other nonmammalian species, and 2) the potential motoneuronal innervation of slow-tonic fibers in turtle hindlimb muscles.
 ...
PMID:Slow-tonic muscle fibers and their potential innervation in the turtle, Pseudemys (Trachemys) scripta elegans. 1573 49

Enzymatically dissociated flexor digitorum brevis (FDB) and soleus fibres from mouse were used to compare the kinetics of electrically elicited Ca2+ transients of slow and fast skeletal muscle fibres, using the fast Ca2+ dye MagFluo4-AM, at 20-22 degrees C. For FDB two Ca2+ transient morphologies, types I (MT-I, 11 fibres, 19%) and II (MT-II, 47 fibres, 81%), were found, the kinetic parameters (amplitude, rise time, half width, decay time, and time constants of decay) being statistically different. For soleus (n = 20) only MT-I was found, with characteristics similar to MT-I from FDB. Correlations with histochemically determined mATPase, reduced nicotinamide adenine dinucleotide diaphorase and alpha-glycerophosphate dehydrogenase activities, as well as immunostaining and myosin heavy chain electrophoretic analysis of both muscles suggest that signals classified as MT-I may correspond to slow type I and fast IIA fibres while those classified as MT-II may correspond to fast IIX/D fibres. The results point to the importance of Ca2+ signaling for characterization of muscle fibres, but also to its possible role in determining fibre function.
 ...
PMID:Different fibre populations distinguished by their calcium transient characteristics in enzymatically dissociated murine flexor digitorum brevis and soleus muscles. 1954 97