Giant muscle fibres in pigs with different Ryr1 genotype

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.

Histological aspects of skeletal muscle fibers splitting of C57BL/6NCrl mice

The objective of the current study is to present data on the splitting of skeletal muscle fibers in C57BL/6NCrl mice. Skeletal muscles (m. rectus femoris (m. quadriceps femoris)) from 500 (250 female and 250 male) C57BL/6NCrl mice in the 16th week of life were sampled during autopsy and afterwards standardly histologically processed. Results show spontaneous skeletal muscle fiber splitting which is followed by skeletal muscle fiber regeneration. One solitary skeletal muscle fiber is split, or is in contact with few localized splitting skeletal muscle fibers. Part of the split skeletal muscular fiber is phagocytosed, but the remaining skeletal muscular fiber splits are merged into one regenerating skeletal muscle fiber. Nuclei move from the periphery to the regenerating skeletal muscle fiber center during this process. No differences were observed between female and male mice and the morphometry results document < 1 % skeletal muscle fiber splitting. If skeletal muscular fibers splitting occurs 5 % > of all skeletal muscular fibers, it is suggested to describe and calculate this in the final histopathological report.

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.

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.

Effect of Breed and Age on Histopathological Changes in Pig M. Semimembranosus

The aim of the study was to determine the type and extent of histopathological changes in m. semimembranosus of Polish Landrace (PL), Polish Large White (PLW), Duroc, Pietrain, and Puławska pigs at 60, 90, 120, 150, 180 and 210 days of age. Changes in fibre size (atrophy, hypertrophy - giant fibres), changes in fibre shape (angular fibres), degenerative lesions (necrosis with phagocytosis) and connective tissue hypertrophy were evaluated. The presence of giant fibres was the only histopathological change observed in all age groups of PL, PLW, Duroc and Pietrain pigs, with the percentage of pigs with this type of pathology and the frequency of giant, atrophic and angular fibres increasing significantly with age. In Puławska pigs, giant fibres were only found in the oldest pigs aged 210 days. In these animals, giant fibres as well as atrophic fibres (at 180 and 210 days of age) and angular fibres (at 120, 150, 180 and 210 days of age) occurred in the smallest number of animals and were least extensive. Meanwhile, Pietrain pigs were characterized by a greater number of animals, a significantly greater proportion of giant fibres in all analysed age groups, and a greater proportion of atrophic fibres at 180 and 210 days of age compared to the other pig breeds under analysis. For connective tissue hypertrophy and necrosis with phagocytosis, the changes were not extensive. It is concluded that both the advancing age of the animals and selection of the pigs for increased leanness significantly increases the incidence of histopathological changes in muscle tissue, which may directly translate into pork quality.

The influence of giant fibres on utility for production of massaged products of porcine muscle longissimus dorsi

Musculus longissimus dorsi (L) originating from 6 genotype groups of pigs was examined. Three among these were parental lines: Pietrain (Pi), Duroc (D), Polish Large White x Polish Landrace (PLW x PL), the other three crossbreeds obtained by crossing the aforementioned parental lines: (PLW x PL) x Pi, (PLW x PL) x (PixD) and (PLW x PL) x (D x Pi). It was found that there exists a variety of numbers and sizes of giant fibres and sizes of muscle fibres in the L muscle of the groups of animals, which results in a diversity of quality and susceptibility to massaging. The largest number of giant fibres and the greatest sizes of normal and giant fibres, along with the largest losses after heat treatment, the highest hardness, shear force, the lowest juiciness and attractiveness were found in the L muscle of Pi. Muscle of this breed was characterised by the least change in quality indicators during massaging. The decrease of Pi breed genes in the crossbreed genotype, resulted in reduction in the quantity of giant fibres and fibre sizes in comparison with pure Pi breed, which increased quality of crossbreeds' muscles and their susceptibility to massaging.