A Study on Ovine Muscle Development

ABSTRACT The ontogeny of ovine muscle was studied. 23 single fetuses aged between 48 and 125 days of gestation (dg) were collected from abattoirs. The weight and crown-rump length of fetuses were measured and gestational age was estimated. Semitendinosus muscle (ST) or hind limbs (for smallest fetuses) were dissected and stained for alkali-stable ATPase and slow myosin heavy chain (MHC) antibody and also examined under the electron microscope (EM). Based on histochemical, immunohistochemical and electron microscopy study, qualitative findings were obtained. The results suggested that some secondary fibres early express slow MHC. These small, slow expressing secondary fibres adjacent to the large, slow expressing primary fibres began to occur at 52 dg and these increased in size at around day 69 and then migrated around 87 dg to act as a scaffold for the next generation of secondary (tertiary) fibres. We conclude that some of the large, central, slow expressing (also less intensely stained with alkali-ATPase) fibres at near term sheep fetus might be secondary fibres. Key Words: Muscle, sheep, ontogeny, myogenesis OZET KOYUNDA KAS GELIŞIMI UZERINE BIR CALIŞMA Koyunda kas ontojenisi uzerine calisildi. Gebelik yaslari (gy) 48 ile 125 arasinda degisen 23 adet tekiz fotus mezbahadan toplandi. Fotuslarin agirliklari ve bas-kuyruk mesafeleri olculerek gebelik yaslari tahmin edildi. Semitendinosus kasi (ST) veya cok kucuk olan fotuslardan tum arka bacak disekte edilerek alkali- adenozin trifosfataz (ATPaz) ve yavas-miyozin agir zincir (MHC) antikoru ile boyandi. Ayrica, kesitler elektron mikroskopta (EM) incelendi. Histokimyasal, immunohistokimyasal ve EM calismalarina dayanarak kalitatif bulgular elde edildi. Sonuclar, bazi sekonder liflerin cok erken donemde yavas MHC ekspresyonu yaptiklarini gosterdi. Buyuk, yavas MHC eksprese eden primer liflerin cevresinde olusan bu kucuk, yavas MHC ekspresyonu yapan sekonder lifler 52. gunde olusmaya baslar; yaklasik 69. gunde caplari iyice artar ve yaklasik 87. gunde goc ederek ikinci generasyon sekonder liflerin (tersiyer) olusumu icin cerceve gorevi gorurler. Gelismis gec donem koyun fotusunda gorulen buyuk, merkezi ve yavas MHC eksprese eden (alkali ATPaz ile dusuk yogunlukta da boyanan) liflerin bir kisminin aslinda sekonder lifler olabilecegi sonucuna varildi. Anahtar Kelimeler: Kas, koyun, ontojeni, miyogenez