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Summary -The ultrastructural localization of glucose-6-phosphatase activity and glycogen were investigated in the longissimus dorsi and biceps femoris muscles of normal and splaylegged newborn piglets. Significant differences were ascertained in the distribution of the reaction product of glucose-6-phosphatase activity between the two groups of animals. A fine precipitate was found in the sarcoplasmic reticulum and in the perinuclear cisternae of normal piglet muscles. In splaylegged muscles, variable deposits of coarse reaction product were observed within the extremely dilated cistemae of sarcoplasmic reticulum at their periphery. Moreover, both longitudinal and transversal ultrathin sections of these muscles showed a reduced number of myofibrils and an increased accumulation of glycogen (especially within the large extramyofibrillar spaces) in comparison with muscles of normal piglets. splayleg / muscle ultrastructure / glucose-6-phosphatase / glycogen / pig Résumé ― Démonstration ultrastructurale de l'activité glucose-6-phosphatase et du glycogène dans les muscles squelettiques de porcelets nouveau-nés atteints du syndrome d'abduction des membres. La localisation ultrastructurale de l'activité glucose-6-phosphatase et du glycogène a été analysée dans des muscles (longissimus dorsi et biceps femoris) de porcelets nouveau-nés normaux ou atteints du syndrome. Des différences significatives ont été mises en évidence dans la distribution du produit de réaction de la glucose-6-phosphatase entre les deux groupes d animaux. Un fin précipité a été observé dans le réticulum sarcoplasmique et l'espace périnucléaire dans les muscles de porcelet témoin. Dans les muscles anormaux, des dépôts variables et grossiers du produit de réaction ont été localisés dans les vésicules très dilatées du réticulum sarcoplasmique. De

An inhibition reactivation technique was used for histochemical staining of human skeletal muscle sections. Myofibrillar ATPase activity was inhibited by sodium hydroxymercuribenzoate (2.5 mM in 0.1 M Tris-HCl buffer, pH 7.2-7.5, 30 min) and successively reactivated by cysteine which was added to incubation solution (10 mM cysteine-HCl, 2.5 mM ATP-disodium salt, 50 mM potassium chloride and 27 mM calcium chloride in barbital buffer, pH 9.4, 35 min at 37 C). This technique allows the distinction of three fiber categories with different staining intensities in single cross-section. Dark, intermediate and light fibers correspond to IIB, I, and IIA types, respectively. Storage of air dried sections in the freezer at -20 C for one month had no influence on staining characteristics.

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