The occurrence and histochemical characterization of giant fibers in the muscle of growing and adult animals

Transformation of highly marbled meats under various cooking processes

Cooking induces modifications in meat structure and composition, affecting its sensory and nutritional properties. These changes depend on the cooking method and meat characteristics. In the present study, beef were cooked in three different ways-grilling, boiling, and sous-vide cooking-with two endpoint temperatures, 55 °C and 77 °C, to better understand the general impact of cooking on the structure of fatty meat. Light microscopy was used to visualize muscle, connective, and adipose tissues. After cooking, muscle fibers were more compact, which can be attributed to perimysium shrinkage and water transfer, for all cooking processes except grilling at 55 °C. The cross-sectional area of muscle fibers was not impacted by cooking, regardless of the temperature or cooking method. Connective tissue between adipocytes was affected by cooking at 77 °C, but not at 55 °C. Despite the cooking method used, cooking to well-done (77 °C) clearly affected the structure of the perimysium of beef, possibly because of collagen denaturation.

The occurrence of giant fibres in different muscles of two chicken genotypes

1. The occurrence of Giant Fibres (GF) in three muscles (Pectoralis major (PM), Iliotibialis lateralis and Semimembranosus) with different types of energy metabolism was studied in slow- and fast-growing chicken strains. 2. A total of 20 one-day-old Leghorn chicks (slow-growing) and 20 broiler (Ross 508) chicks (fast-growing) were reared to 100 and 45 d, respectively. 3. A small percentage of GF was seen in pre rigor muscle samples even at 3 min post mortem in both genotypes and in all muscle types studied. 4. From 3 min to 24 h post mortem GF increased both in Leghorn and broiler chickens but to a different extent according to muscle type and genotype. 5. The highest GF 24 h post mortem value was found in the PM muscles belonging to the fast-growing broiler line. 6. It was concluded that every type of muscle can develop GF, but this phenomenon is more evident in the PM especially in animals selected for increased growth rate.

Effects of sustanon on the distribution of satellite cells and the morphology of skeletal muscle fibers during maturation

Sustanon is one of the most commonly used anabolic androgenic drugs to increase skeletal muscle mass and strength. This drug is a blend of four esterized testosterone derivatives: Testosterone propionate, testosterone phenylpropionate, testosterone isocaproate and testosterone decanoate. Little is known about the effects of this drug on skeletal muscle at the cellular level. This study aimed to investigate the influence of Sustanon on the morphology of skeletal muscle fibers and the distribution of myogenic stem cells known as Satellite Cells (SCs) during postnatal growth. We hypothesized that Sustanon-induced skeletal muscle hypertrophy is associated with an increase in the number of SCs. Robust immunocytochemical techniques and morphometric analyses were used to calculate the numbers of SCs and myonuclei within the pectoralis muscle of chickens. Also, DNA concentration and Pax7 protein levels were measured to confirm immunocytochemical findings. Sustanon significantly increased pectoralis mass and fiber size. All SC indices and the number of myonuclei increased significantly by Sustanon administration. In addition, greater DNA concentration and Pax7 protein expression were found in Sustanon-treated birds. This study indicates that Sustanon can induce avian skeletal muscle hypertrophy and that this is correlated with increased numbers of SCs and myonuclei.

Characterization of muscle fiber type in the pectoralis major muscle of slow-growing local and commercial chicken strains

The study aimed to characterize muscle fiber type of the pectoralis major muscle of slow-growing chickens belonging to the Padovana local breed, the commercial strain Berlanda gaina, and their cross. Forty-five chickens (both males and females) from the different genotypes were grown up to 180 d. Histochemical and morphometrical analyses were performed to characterize muscle fiber types, myofiber density, and myofiber size of the different genotypes. The effects of genotype, sex, and their interaction were estimated. Muscle samples appeared almost entirely made up of IIB fiber type, whereas a low percentage of area (5 to 6%) was composed of hypercontracted fiber. Myofiber density was significantly higher (P < 0.05) in Padovana strains and cross-sectional area was significantly lower (P < 0.01) than in Berlanda strain. Muscle fiber characteristics appeared not to be affected by the interaction of genotype × sex.

Histochemical properties of fibre types in muscles of wild and domestic pigs and the effect of growth rate on muscle fibre properties

This study reports the results of a comparison of the histochemical properties of various types of porcine muscles in wild and domestic pigs. In domestic pigs, the influence of growth rates on these properties were studied in five muscles: longissimus dorsi (LD), semimembranosus (SM), gluteus superficialis (GS), infra spinam (IS) and masseter (MAS). The growth rate was expressed as: (i) live weight (LW) at 165±2 days and (ii) daily LW gain from day 88 to day 165 (DG) on the experimental diet. LD, SM, GS and IS of wild pigs were found to contain a higher area percentage of oxidative type IIA fibres (type IIA%(area)) and a lower percentage area of glycolytic type IIB fibres (type IIB%(area)) than the same muscles of domestic pigs. The capillary density in the light muscles (LD, SM, GS) of wild pigs was twice that of domestic pigs, indicating higher oxidative capacity. In domestic pigs the cross sectional area of type IIB fibres (CSA(IIB)) was markedly larger than the cross sectional area of type I (CSA(I)) and IIA (CSA(IIA)) fibres. The average fibre cross sectional area (CSA(fibre)) was about the same in the muscles of wild and domestic pigs except in LD and SM, where the average fibre cross sectional area was approximately 25% smaller in wild pigs than in domestic pigs. This difference was caused by the large cross sectional area of type IIB fibres in the light muscles of domestic pigs. In the light muscles of domestic pigs, the cross sectional area of type IIA fibres increased most with increasing growth rate. Growth rate influences muscle fibre properties only in light muscles, not in dark muscles.

"Giant" muscle fibres in skeletal muscle of normal pigs

Observations made during a growth and development study of the semitendinosus and trapezius muscles of 49 purebred Large White pigs between birth and 128 days of age revealed the presence of giant fibres. The occurrence, histochemical and ultrastructural properties of these giant fibres were investigated. A high proportion of the pigs (85 per cent) contained giant fibres in their muscles but these giant fibres usually represented less than 1 per cent of the total myofibre population. Giant fibres possessed enhanced adenosine triphosphatase activity and a high capacity for oxidative metabolism (indicated by succinate dehydrogenase activity) which was reflected ultrastructurally by the greatly heightened electron density of myofibrils and by an abnormally high percentage of mitochondria and lipid droplets. These deviations from normal muscle fibre composition, together with the reduced percentage volume of sarcoplasmic reticulum, were consistent with changes seen in functionally over-loaded muscle. It appears that giant fibre anomalies occur through increased activity stimulated in occasional muscle fibres, perhaps by a structural defect, such as an inadequate amount of sarcoplasmic reticulum, which causes hyper-contractile activity within the fibres and associated compensatory adaptations. Giant fibres did not appear to represent fibres undergoing degenerative changes.

Motoneurons of M. semitendinosus in domestic and wild pigs. A horseradish peroxidase and cord-survey study

In domestic and wild pigs motor nuclei of the M. semitendinosus were labelled by retrograde transport of horseradish peroxidase (HRP) from muscle to spinal cord. Further motoneurons in the lumbosacral cord were stained with Luxol-fast-blue and cresyl violet. Motoneurons innervating M. semitendinosus were present in the ventral horns of the last (6th) lumbal and the first sacral cord segments. They were localized within two motor columns lying parallel to each other in the medial and lateroventral position. Both parts of the semitendinosus motor nuclei showed a spindle-like shape with both cranial and caudal enlargements. Localization, extent, and shape of the semitendinosus motor nuclei were similar in domestic and wild pigs. The average motoneuron diameter was larger in domestic than in wild pigs. The lumbosacral cord of the wild pig was thicker than that of the domestic pig. It is suggested that the size of alpha-motoneurons has increased as a result of selective breeding after domestication. This process might correlate with a higher incidence of myopathies in domestic pigs.