Giant Muscle Fibres in Pigs with Different Ryr1 Genotype

Abstract

This study examined the frequency, morphological and immunohistochemical characteristics of the giant fibres in the longissimus muscle of local Krsko polje pigs with different Ryr1 genotypes. Giant fibres were round-shaped and had significantly increased cross-sectional area compared with normal muscle fibres. Only fast-twitch glycolytic fibres were affected, usually showing enhanced succinate dehydrogenase activity. On the ultrastructural level, the dilation of the sarcoplasmic reticulum, swelling of mitochondria and destruction of myofilaments was observed. The incidence of giant fibres was the highest in Ryr1 dimutant pigs (Ryr1 nn), which also exhibited lower muscle pH1 than heterozygous (Ryr1 Nn) or pigs with the wild Ryr1 gene (Ryr1 NN). However, the giant fibres were also present in pigs free of Ryr1 gene mutation. Our results suggest that the giant fibre syndrome depends mostly upon the rate and intensity of early post-mortem glycolysis, which results in acidity of muscle tissue. We suppose that the giant fibre formation is a result of excessive intracellular lactate accumulation in some fast-twitch glycolytic fibres. This process could also explain the ultrastructural alterations and the consequent changes in the oxidative enzymes and myofibrillar ATPase staining pattern observed in our and some previous studies.

Skeletal Myocyte Types and Vascularity in the Black Sicilian Pig

“…Trapezius muscle is an abductor of the shoulder; its cervical portion pulls on the scapula in dorsocranial direction, its thoracic portion aids this movement by oscillating the dorsal part of the scapula in caudal direction. In agreement with the study of Fazarinc et al (2002), our study shows that the longissimus muscle is a typical white muscle in which fast-twitch glycolytic fibres dominate. It has been suggested that muscles with a high density of anaerobic fibres have a higher probability of being of poor eating quality, due to the more rapid accumulation of lactate and decline in pH (Van Laack et al 2001).…”

“…Muscle fibre hypertrophy occurs in animals in cases of congenital neuromuscular diseases and nutritional dystrophies, conditions that result in compensatory hypertrophies of some muscle fibres (Jubb et al 1985). In a study on local Kr‰ko polje pigs, Fazarinc et al (2002) reported the occurrence of giant fibres in porcine longissimus muscle is strongly correlated with the muscle pH, an indicator of early post-mortem glycolysis, leading to lactate formation in the tissue. Lactate is osmoticly active, binding intercellular water, which results in interstitial oedema and PSE condition of the muscle.…”

“…The aim of this study was to evaluate the effect of sex on the histochemical and morphometric characteristics of muscle fibres on the basis of myosin ATPase, succinic dehydrogenase, and to determine the presence of giant fibres in the muscles considered. Such fibre types are distinctly enlarged and rounded with two to three times greater cross-sectional area than normal fibres (Fazarinc et al 2002), they are found predominantly in the white muscles and in pale soft and exudative (PSE) meat. To visualize the blood capillaries the α-amylase-PAS methods was used; such reaction stains the basal membrane of the capillaries.…”

New Insights into Muscle Fibre Types in Casertana Pig

“…Giant fibres are characterized by swollen appearance and also show different histochemical staining pattern (Fazarinc et al 2002). However, apparently giant fibres do not occur in all pig breeds; they were not apparent in Black Sicilian pigs (Velotto et al 2007).…”

Characterization of Muscle Fibre Type and Evaluation of the Presence of Giant Fibres in Two Meat Chicken Hybrids

“…They are usually rounded in shape, larger than normal fibres and stain darker when coloured with haematoxylin-eosin. Giant fibres were first studied by Cassens et al (1969) and since then various authors have taken them into consideration, especially in swine where there seemed to be a connection between their presence and the PSE condition (Fazarinc et al, 2002;Severini and Loschi, 1997). This topic has recently also been considered in turkeys and chicken (Remignon et al, 2000;Mammoli et al, 2004).…”