Fatores de crescimento coordenam múltiplas vias de sinalização durante o desenvolvimento embrionário. Neste estudo, a abundância de mRNA dos genes IGF-II e bFGF foi estimada em embriões de galinha por análises de RT-PCR competitiva. Aumentos na abundância de mRNA de IGF-II foram observados nos estádios HH1, 5. Os níveis de mRNA de bFGF exibiram aumentos a partir dos estádios HH18 e 20, seguido por uma acentuada redução a níveis basais no estádio HH24 e por um segundo pico na expressão destes transcritos no estádio HH26. Tais descobertas proporcionam importantes informações sobre o padrão de expressão destes fatores de crescimento durante a embriogênese de aves

In this study, the abundance of IGF-II and bFGF transcripts was estimated in the chicken embryos using the competitive RT-PCR analysis. Significant enhancements in the abundance of IGF-II mRNA were observed at stages HH1 and 5, and a new accumulation in these levels was observed at stage HH18 in comparison to the basal levels. The abundance of bFGF mRNA increased significantly at stages HH18 and 20, followed by an upregulation in the expression of these transcripts at stage HH26. These findings provided important information about the temporal expression pattern of IGF-II and bFGF transcripts in the whole chicken embryos during in ovo development.

This report describes the transcription apparatus of Mycoplasma hyopneumoniae (strains J and 7448) and Mycoplasma synoviae, using a comparative genomics approach to summarize the main features related to transcription and control of gene expression in mycoplasmas. Most of the transcription-related genes present in the three strains are well conserved among mycoplasmas. Some unique aspects of transcription in mycoplasmas and the scarcity of regulatory proteins in mycoplasma genomes are discussed.

The hepatic expression and plasma concentrations of IGF-I were investigated in three broiler chicken strains selected for different growth rates (HP-Hubbard-Pettersen, a fast growing strain; NN-Naked-neck, a strain with an intermediate growth rate and a heterozygous genotype, and C-Caipira, a slow growing crossbred strain). The chickens were studied at 1, 21 and 42 days of age and had free access to food throughout the study. Hepatic IGF-I mRNA expression was assessed by dot blot analysis using a randomly labeled chicken IGF-I cDNA as the probe and plasma IGF-I concentrations were assayed by radioimmunoassay. The hepatic levels of IGF-I mRNA increased from 1 to 21 days of age in all strains, with NN chickens showing a higher (p < 0.05) IGF-I expression than the other strains. Plasma IGF-I concentrations increased (p < 0.05) with broiler chicken age, but there were no significant differences among the strains. These results indicate that despite differences in the growth rates among the strains, the changes in the expression of IGF-I mRNA in liver and in the plasma levels of IGF-I were independent of broiler chicken strain, but varied with chicken age.