RESUMO
This study was performed to evaluate breast muscle development in chicken genotypes divergently selected for muscularity. In the first experiment, 2 commercial broiler lines (a high breast yield, HBY, and a normal breast yield broiler strain-cross, NBY) and a Leghorn line were grown up to 35 d to evaluate BW, breast weight, and breast yield. At 7 and 21 d of age, pectoralis muscle was used to estimate myofiber density (MFD, number of myofibers per mm2) and total apparent myofiber number (MFN). In the second experiment, the ontogeny of myostatin was determined from broiler- and Leghorn-type chick embryos, at embryonic days 1 to 20 (E1 to E20), using reverse transcription (RT)-PCR. As expected, the Leghorn line had lower BW, breast weight, and breast yield than broiler lines. The HBY line showed higher breast yield at all ages evaluated, but lower BW at 21 and 35 d than the NBY line. The Leghorn line had 45% higher MFD than broilers, which indicates an increased cross-sectional area of the myofibers in broiler lines. No MFD difference was observed between the broiler strains (P > 0.05). The myofiber number of broilers was more than twice that of Leghorns and HBY had 10% higher MFN than the NBY line. Myofiber number was correlated to BW (r = 0.58), breast weight (r = 0.58), and breast yield (r = 0.69). Conversely, MFD showed negative correlation with BW, breast weight, and breast yield (r = -0.85, -0.83, and -0.88, respectively). No effect of genotype or interaction between genotype and embryonic age was observed for myostatin expression. This study showed that broilers have higher MFN in the breast muscles than Leghorn-type chickens, and that high breast yield of broiler strains may be due to increased MFN. Higher muscularity of broilers, as compared with Leghorns, was not attributed to lower expression of myostatin during embryonic development.
Assuntos
Galinhas/genética , Genótipo , Fibras Musculares Esqueléticas/ultraestrutura , Músculo Esquelético/ultraestrutura , Fator de Crescimento Transformador beta/biossíntese , Animais , Peso Corporal , Embrião de Galinha/química , Embrião de Galinha/crescimento & desenvolvimento , Cruzamentos Genéticos , Feminino , Expressão Gênica , Masculino , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/metabolismo , Miostatina , Tamanho do Órgão , Músculos Peitorais/crescimento & desenvolvimento , Músculos Peitorais/metabolismo , Músculos Peitorais/ultraestrutura , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Especificidade da Espécie , Fatores de Tempo , Fator de Crescimento Transformador beta/genéticaRESUMO
Bioassays were performed to assess the effects of different levels of growth medium supplementation with fetal bovine serum (FBS), fish fry extract (FE), combinations of FBS and FE, and addition of insulin-like growth factor I (IGF-I) and fibroblast growth factor (FGF) on the proliferation of brown bullhead catfish cells (BB line). Treatments (n = 4) were: 2.5, 5, 10, and 15.0 FBS or FE and 5/2.5, 5/5, 10/2.5, and 10/5 of a FBS/FE combination as supplement to the growth medium, or the addition of 0.1, 1, 2.5, 10, 25, and 75 ng/ml of either IGF-I or FGF to the growth media. Initial cell density was 1.1 x 10(6) cells per well on uncoated 24-well plates. Incubation temperature was 29.5 +/- 0.7 degrees C. Six hours after plating, initial culture medium was removed, plates rinsed with Dulbecco's phosphate buffered saline, treatment media added, and cells allowed to proliferate for 24 hours. Another bioassay was performed with rat myoblast omega cells (RMo) using the same levels of growth medium supplemented with FBS, FE and FBS/FE. Base growth medium was Dulbecco's MEM. The initial cell density was 7.2 x 10(6) cells per well, and the bioassay was carried out at 36.0 +/- 0.5 degrees C, on a 95 air, 5 CO2 incubator. Increasing levels of FBS had a positive effect (P < 0.05) on the proliferation of both BB and RMo cells. Increasing levels of FE had a negative effect (P < 0.05) on the proliferation of BB cells and totally inhibited the proliferation of RMo cells at any level of supplementation. Higher levels of FE on the FBS/FE combinations presented a negative effect on the proliferation of both BB and RMo cells (P < 0.05). Insulin-like growth factor I had a positive quadratic effect (P < 0.05) on the proliferation of BB cells. Apparently, mammalian growth factors slightly stimulated mitogenic activity in fish cells, while FE contained factors which inhibited the mitogenic activity of RMo and BB cell lines.
Assuntos
Animais , Bovinos , Ratos , Sangue Fetal , Fatores de Crescimento de Fibroblastos , Ictaluridae , Fator de Crescimento Insulin-Like I , Mitógenos/farmacologia , Extratos de Tecidos , Bioensaio , Linhagem Celular , Meios de Cultura , Divisão Celular/efeitos dos fármacos , Óvulo/fisiologiaRESUMO
Bioassays were performed to assess the effects of different levels of growth medium supplementation with fetal bovine serum (FBS), fish fry extract (FE), combinations of FBS and FE, and addition of insulin-like growth factor I (IGF-I) and fibroblast growth factor (FGF) on the proliferation of brown bullhead catfish cells (BB line). Treatments (n = 4) were: 2.5, 5, 10, and 15.0% FBS or FE and 5/2.5, 5/5, 10/2.5, and 10/5 of a FBS/FE combination as supplement to the growth medium, or the addition of 0.1, 1, 2.5, 10, 25, and 75 ng/ml of either IGF-I or FGF to the growth media. Initial cell density was 1.1 x 10(6) cells per well on uncoated 24-well plates. Incubation temperature was 29.5 +/- 0.7 degrees C. Six hours after plating, initial culture medium was removed, plates rinsed with Dulbecco's phosphate buffered saline, treatment media added, and cells allowed to proliferate for 24 hours. Another bioassay was performed with rat myoblast omega cells (RMo) using the same levels of growth medium supplemented with FBS, FE and FBS/FE. Base growth medium was Dulbecco's MEM. The initial cell density was 7.2 x 10(6) cells per well, and the bioassay was carried out at 36.0 +/- 0.5 degrees C, on a 95% air, 5% CO2 incubator. Increasing levels of FBS had a positive effect (P < 0.05) on the proliferation of both BB and RMo cells. Increasing levels of FE had a negative effect (P < 0.05) on the proliferation of BB cells and totally inhibited the proliferation of RMo cells at any level of supplementation. Higher levels of FE on the FBS/FE combinations presented a negative effect on the proliferation of both BB and RMo cells (P < 0.05). Insulin-like growth factor I had a positive quadratic effect (P < 0.05) on the proliferation of BB cells. Apparently, mammalian growth factors slightly stimulated mitogenic activity in fish cells, while FE contained factors which inhibited the mitogenic activity of RMo and BB cell lines.